SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Concentration risks (Details)	12 Months Ended
Dec. 31, 2021 USD ($) customer	Dec. 31, 2020 USD ($) customer	Dec. 31, 2019 USD ($) customer
Concentration risks
Aggregate dollar amount of net sales to significant customers	$ 188,382,454	$ 81,862,453	$ 41,797,179
Allowance for doubtful accounts	$ (150,000)
Customer Concentration Risk \| Revenue \| Significant customers
Concentration risks
Number of significant customers \| customer	1	2	3
Aggregate dollar amount of net sales to significant customers	$ 113,700,000	$ 41,600,000	$ 19,000,000.0
Percentage of net sales to significant customers	60.30%	50.60%	45.60%
Supplier Concentration Risk \| Revenue \| China
Concentration risks
Percentage of net sales to significant customers	92.00%	85.20%	82.60%

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Amount of increase (decrease) in allowance for credit loss on accounts receivable.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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