Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (8,136)	$ (7,220)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	64	56
Noncash interest expense	156	134
Amortization of intangible assets	76	76
Inventory excess and obsolescence charge	582	405
Stock-based compensation expense	694	449
Change in operating assets and liabilities:
Accounts receivable, net	(112)	781
Inventory	(1,360)	(617)
Prepaid expenses and other assets	349	544
Accounts payable	312	(1,261)
Accrued expenses and other current liabilities	(1,193)	(692)
Foreign currency remeasurement (gain) loss	(17)	38
Net cash used in operating activities	(8,585)	(7,307)
Cash flows from investing activities:
Proceeds from the sale and maturity of short-term investments		4,000
Purchase of property and equipment	(22)	(68)
Net cash (used in) provided by investing activities	(22)	3,932
Cash flows from financing activities:
Payment of initial public offering costs		(522)
Proceeds from exercise of stock options	36	8
Net cash provided by (used in) financing activities	36	(514)
Effect of exchange rate on cash and cash equivalents	6	(2)
Net decrease in cash and cash equivalents	(8,565)	(3,891)
Cash and cash equivalents, beginning of period	74,394	45,302
Cash and cash equivalents, end of period	65,829	41,411
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	733	745
Supplemental disclosures of noncash investing and financing activities:
Property and equipment in accounts payable		4
Issuance of common stock for early exercised stock options		$ 1
Reclassification of liability-classified stock-based compensation to equity-classified	$ 82