Document and Entity Information Statement [Table] Statement [Line Items] Statement SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Common Stock, Shares Outstanding Entity Emerging Growth Company Entity Ex Transition Period Entity Shell Company Document Fiscal Year Focus Document Fiscal Period Focus CONSOLIDATED BALANCE SHEETS Assets [Abstract] Assets, Current [Abstract] Current assets Cash Cash Amount of term deposits with banks, which have original maturities of three months or less and are readily convertible to known amounts of cash. Term Deposits with Banks Term deposit Restricted Cash, Current Restricted cash-current Debt Securities, Available-for-sale, Current Aggregate fair value Short-term investments Accounts Receivable, Net, Current Accounts receivable, net Accounts Receivable, net Accounts receivable Inventory, Net Inventories Inventories Prepaid Expense and Other Assets, Current Prepayments and other current assets Prepayments and Other Current Assets Assets, Current Total current assets Assets, Noncurrent [Abstract] Non-current assets Restricted Cash, Noncurrent Restricted cash-non current Property, Plant and Equipment, Net Property and equipment, net Property and Equipment, net Finite-Lived Intangible Assets, Net Intangible asset, net Net carrying amount Intangible assets, net Other Assets, Noncurrent Other non-current assets Other non-current assets Assets, Noncurrent Total non-current assets Assets Total assets Liabilities. Liabilities, Current [Abstract] Current liabilities Short-term Bank Loans and Notes Payable Short-term bank borrowings (including short-term bank borrowings of VIE without recourse to the Company of RMB168,234,207 and RMB179,978,003 as of December 31, 2017 and 2018, respectively) Short-term bank borrowings Convertible Debt, Current Convertible loan Accounts Payable, Current Accounts payable (including accounts payable of VIE without recourse to the Company of RMB124,937,465 and RMB249,665,890 as of December 31, 2017 and 2018, respectively) Accounts payable Carrying value as of the balance sheet date of advances from customers. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Advances from Customers, Current Advances from customers (including advances from customers of VIE without recourse to the Company of RMB48,503,389 and RMB20,505,861 as of December 31, 2017 and 2018, respectively) Advances from customers Contract with Customer, Liability, Current Deferred revenue - current (including deferred revenue-current of VIE without recourse to the Company of RMB9,853,361 and RMB12,666,330 as of December 31, 2017 and 2018, respectively) Deferred revenue - current Carrying value as of the balance sheet date of accrued expenses and other liabilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Expenses and Other Liabilities, Current Accrued expenses and other current liabilities (including accrued expenses and other current liabilities of VIE without recourse to the Company of RMB75,382,869 and RMB119,242,975 as of December 31, 2017 and 2018, respectively) Accrued expenses and other current liabilities Accrued expenses and other current liabilities Liabilities, Current Total current liabilities Liabilities, Noncurrent [Abstract] Non-current liabilities Standard Product Warranty Accrual, Noncurrent Warranty-non current (including warranty-non current of VIE without recourse to the Company of RMB12,378,751 and RMB17,609,842 as of December 31, 2017 and 2018, respectively) Warranty - non current Contract with Customer, Liability, Noncurrent Deferred revenue - non current (including deferred revenue-non current of VIE without recourse to the Company of RMB144,700 and RMB234,801 as of December 31, 2017 and 2018, respectively) Deferred revenue - non current Liabilities, Noncurrent Total non-current liabilities Liabilities Total liabilities Temporary Equity [Abstract] MEZZANINE EQUITY Temporary Equity, Carrying Amount, Attributable to Parent Balance at end Balance at beginning Total mezzanine equity Stockholders' Equity Attributable to Parent [Abstract] SHAREHOLDERS' (DEFICIT) / EQUITY: Common Stock, Value, Issued Ordinary Shares Ordinary shares Preferred Stock, Value, Issued Series Seed Convertible Preferred Shares (US$0.0001 par value, 30,000,000 and nil shares authorized, issued and outstanding as of December 31, 2017 and 2018) Series Seed Convertible Preferred Shares Additional Paid in Capital Additional paid-in capital Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income/(loss) Retained Earnings (Accumulated Deficit) Accumulated deficit Stockholders' Equity Attributable to Parent Ending balance Beginning balance Total shareholders' (deficit)/equity Liabilities and Equity Total liabilities, mezzanine equity and shareholders' (deficit)/equity Temporary Equity, Par or Stated Value Per Share Redeemable Convertible Preferred Shares, par value (in dollars per share) Temporary equity value per share Temporary Equity, Shares Authorized Redeemable Convertible Preferred Shares, authorized Temporary Equity, Shares Issued Redeemable Convertible Preferred Shares, issued Temporary Equity, Shares Outstanding Redeemable Convertible Preferred Shares, outstanding Outstanding temporarily equity (in shares) Temporary Equity, Aggregate Amount of Redemption Requirement Redemption value Temporary Equity, Liquidation Preference Liquidation value Common Stock, Par or Stated Value Per Share Ordinary shares, par value (in dollars per share) Common Stock, Shares Authorized Ordinary shares, authorized Common Stock, Shares, Issued Ordinary shares, issued Common Stock, Shares, Outstanding Ordinary shares, outstanding Preferred Stock, Par or Stated Value Per Share Series Seed Convertible Preferred Shares, par value (in dollars per share) Preferred Shares, par value (in dollars per share) Preferred Stock, Shares Authorized Series Seed Convertible Preferred Shares, authorized Preferred shares, authorized Preferred Stock, Shares Issued Series Seed Convertible Preferred Shares, issued Preferred shares, issued Preferred Stock, Shares Outstanding Series Seed Convertible Preferred Shares, outstanding Preferred shares, outstanding CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS Revenue from Contract with Customer, Excluding Assessed Tax Net revenues Cost of Revenue Cost of revenues Gross Profit Gross (loss)/profit Operating Expenses [Abstract] Operating expenses: Selling and Marketing Expense Selling and marketing expenses Research and Development Expense Research and development expenses General and Administrative Expense General and administrative expenses Operating Income (Loss) Operating loss Amount of realized and unrealized gain (loss) on convertible loan. Change in Fair Value of Convertible Loan Change in fair value of a convertible loan Change in fair value of a convertible loan Changes in fair value of a convertible loan Interest Expense Interest expenses Investment Income, Interest Interest income Gain (Loss) on Investments Investment income Investment income Foreign Currency Transaction Gain (Loss), before Tax Foreign currency exchange (losses)/gain Amount of government grants. Government Grants Government grants Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest (Loss)/income before income taxes Loss before income taxes Income Tax Expense (Benefit) Income tax expense Actual income tax expense Net Income (Loss) Attributable to Parent Numerator for basic and diluted net loss per share calculation Net loss Net loss Net loss attributable to ordinary shareholders Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive (losses)/income: Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Foreign currency translation adjustment, net of nil income taxes Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments, after Tax Unrealized gain on available for sale securities, net of nil income taxes Unrealized holding gains on available-for-sale security, net of nil income taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Less: reclassification adjustment for gain on available for sale securities realized in net income, net of nil income taxes Reclassification adjustment for gain on available for sale securities realized in net income, net of nil income taxes Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive loss NET LOSS PER ORDINARY SHARE Net loss per ordinary share Earnings Per Share, Basic and Diluted Basic and diluted Weighted Average Number of Shares Outstanding, Diluted [Abstract] Weighted average number of shares outstanding used in computing net loss per ordinary share Denominator: Weighted Average Number of Shares Outstanding, Basic and Diluted Basic and diluted Weighted average number of shares outstanding used in computing net loss per share Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax, Portion Attributable to Parent Foreign currency translation adjustment, income tax Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax Unrealized gain on available for sale securities, income tax Unrealized holding gains on available-for-sale security, income tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Reclassification adjustment for gain on available for sale securities realized in net income, income tax Reclassification adjustment for gains on available-for-sale securities realized in net income, income tax CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' (DEFICIT) / EQUITY Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (decrease) in shareholders' deficit Shares, Outstanding Ending balance (in shares) Beginning balance (in shares) Stock Issued During Period, Value, New Issues Issuance of ordinary shares Stock Issued During Period, Shares, New Issues Issuance of ordinary shares (in shares) Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Share-based compensation Stock Repurchased and Retired During Period, Value Repurchase and retirement of ordinary shares Stock Repurchased and Retired During Period, Shares Repurchase and retirement of ordinary shares (in shares) Number of ordinary shares repurchased Conversion of Stock, Amount Issued Conversion to Series A-3 Preferred Shares Conversion to Ordinary Shares Conversion of preferred shares into ordinary shares Conversion of Stock, Shares Issued Conversion of preferred shares into ordinary shares (in shares) CONSOLIDATED STATEMENTS OF CASH FLOWS Net Cash Provided by (Used in) Operating Activities [Abstract] Operating activities: Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net loss Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash (used in)/provided by operating activities Amount of additions charged to bad debt expense and write-off of bad debt allowance. Allowance for doubtful accounts, Additions to Expense and Write-off of Allowance Allowance (reversals) for doubtful accounts Share-based Compensation. Share-based compensation Depreciation, Depletion and Amortization Depreciation and amortization Foreign Currency Transaction Gain (Loss), Unrealized Unrealized foreign exchange loss Gain (Loss) on Disposition of Property Plant Equipment Loss on disposal of property and equipment Inventory Write-down Inventories write downs Write-down of inventory Amount of interest income from restricted cash. Interest Income on Restricted Cash Interest income from restricted cash Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Accounts Receivable Accounts receivable Increase (Decrease) in Inventories Inventories Increase (Decrease) in Prepaid Expense and Other Assets Prepayments and other current assets Increase (Decrease) in Other Noncurrent Assets Other non-current assets Increase (Decrease) in Accounts Payable Accounts payable The increase (decrease) during the reporting period for advances from customers. Increase (Decrease) in Advances from Customers Advances from customers Increase (Decrease) in Contract with Customer, Liability Deferred revenue Amount of increase (decrease) during the reporting period for warranty, non-current. Increase (Decrease) in Warranty, Non-current Warranty-non current Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities Accrued expenses and other current liabilities Net Cash Provided by (Used in) Operating Activities Net cash used in operating activities Net cash (used in)/provided by operating activities Net cash (used in)/provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Investing activities: Payments to Acquire Property, Plant, and Equipment Cash paid for purchase of property and equipment Payments to Acquire Land Held-for-use Prepayments for land use rights Payments to Acquire Intangible Assets Purchase of intangible assets The cash outflow for acquisition of term deposits. Payments to Acquire Term Deposits Purchase of term deposits Amount of cash inflow from the sale or maturity redemption of term deposits. Proceeds From Maturity Redemption Of Term Deposits Cash received from redemption of term deposits Payments to Acquire Short-term Investments Cash paid for purchase of short-term investments Proceeds from Sale of Short-term Investments Cash received from sale of short-term investments Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Financing activities: Proceeds from Issuance Initial Public Offering Proceeds from issuance of Class A Ordinary Shares upon IPO, net of underwriting commissions and discounts of RMB30,599,667 Payments of Stock Issuance Costs Payment of issuance cost of Class A Ordinary Shares in connection with IPO Proceeds from Issuance of Convertible Preferred Stock Proceeds from issuance of Redeemable Convertible Preferred Shares Payments for Repurchase of Common Stock Cash paid for repurchase of Ordinary Shares Consideration for repurchase of ordinary shares The cash inflow from the restricted stock to the entity. Proceeds from Issuance of Restricted Stock Issuance of Restricted Ordinary Shares The cash outflow for restricted cash paid as collateral for short-term bank borrowings. Restricted Cash Paid as Collateral for Short-term Bank Borrowings Restricted cash paid as collateral for short-term bank borrowings Proceeds from Convertible Debt Proceeds from a convertible loan Issuance of convertible loan Proceeds from Bank Debt Proceeds from short-term bank borrowings Repayments of Bank Debt Repayment for short-term bank borrowings Net Cash Provided by (Used in) Financing Activities Net cash provided by financing activities Net cash provided by financing activities Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Effect of foreign currency exchange rate changes on cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Net increase in cash Net increase in cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash at the end of the year Cash at the beginning of the year Supplemental Cash Flow Information [Abstract] Supplemental information Interest Paid, Excluding Capitalized Interest, Operating Activities Interest paid The amount of payable issuance costs that were incurred during ordinary shares in connection with IPO noncash transaction. Payable For Issuance Cost Of Class A Ordinary Shares In Connection with IPO Payable for issuance cost of Class A Ordinary Shares in connection with IPO The cash outflow for cost incurred with underwriting commissions and discounts. Stock Issuance, Underwriting Commissions and Discounts Underwriting commissions and discounts for issuance of Class A Ordinary Shares upon IPO No definition available. DESCRIPTION OF ORGANIZATION AND PRINCIPAL ACTIVITIES Business Description and Basis of Presentation [Text Block] DESCRIPTION OF ORGANIZATION AND PRINCIPAL ACTIVITIES SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES SHORT-TERM INVESTMENTS Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] SHORT-TERM INVESTMENTS ACCOUNTS RECEIVABLES, NET Loans, Notes, Trade and Other Receivables Disclosure [Text Block] ACCOUNTS RECEIVABLES, NET INVENTORIES Inventory Disclosure [Text Block] INVENTORIES PREPAYMENTS AND OTHER CURRENT ASSETS The entire disclosure for prepayments and other current assets. Prepayments and Other Current Assets Disclosure [Text Block] PREPAYMENTS AND OTHER CURRENT ASSETS PROPERTY AND EQUIPMENT, NET Property, Plant and Equipment Disclosure [Text Block] PROPERTY AND EQUIPMENT, NET INTANGIBLE ASSETS, NET Intangible Assets Disclosure [Text Block] INTANGIBLE ASSETS, NET OTHER NON-CURRENT ASSETS The entire disclosure for other non-current assets. Other Non Current Assets [Text Block] OTHER NON-CURRENT ASSETS SHORT-TERM BANK BORROWINGS AND RESTRICTED CASH Short-term Debt [Text Block] SHORT-TERM BANK BORROWINGS AND RESTRICTED CASH CONVERTIBLE LOAN The entire disclosure for convertible debt. Convertible Debt [Text Block] CONVERTIBLE LOAN No definition available. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES The entire disclosure for accrued expenses and other current liabilities. Accrued Expenses and Other Liabilities, Current [Text Block] ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES No definition available. REDEEMABLE CONVERTIBLE PREFERRED SHARES The entire disclosure for terms, amounts, nature of changes, rights and privileges, dividends, and other matters related to redeemable convertible preferred shares. Series A Redeemable Convertible Preferred Shares [Disclosure Text Block] REDEEMABLE CONVERTIBLE PREFERRED SHARES ORDINARY SHARES AND SERIES SEED PREFERRED SHARES Stockholders' Equity Note Disclosure [Text Block] ORDINARY SHARES AND SERIES SEED PREFERRED SHARES SHARE-BASED COMPENSATION Disclosure of Compensation Related Costs, Share-based Payments [Text Block] SHARE-BASED COMPENSATION FAIR VALUE MEASUREMENT Fair Value Disclosures [Text Block] FAIR VALUE MEASUREMENT INCOME TAX