Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows From Operating Activities
Net income	$ 1,238	$ 3,697
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	170	154
Stock-based compensation	1,014	733
Write-off of deferred costs	57
Write-off of long lived assets		9
Deferred income taxes	(69)	(135)
Changes in operating assets and liabilities:
Accounts receivable	(255)	19
Inventory	338	(245)
Prepaid expenses and other current assets	(31)	(214)
Other assets	(54)	(7)
Accounts payable	259	422
Accrued expenses	401	324
Customer deposits	191	(645)
Other liabilities	17	41
Net cash provided by operating activities	3,276	4,153
Cash Flows From Investing Activities
Purchase of property and equipment	(276)	(145)
Net cash used in investing activities	(276)	(145)
Cash Flows From Financing Activities
Net proceeds from exercise of stock options	367	26
Payments of deferred costs	(57)	(1,355)
Proceeds from initial public offering, net of underwriter commission		8,139
Net cash provided by financing activities	310	6,810
Net increase in cash and cash equivalents	3,310	10,818
Cash and cash equivalents at beginning of period	21,536	10,006
Cash and cash equivalents at end of period	24,846	20,824
Supplemental Disclosure of Cash Flow Information
Cash paid for income taxes	43	1,834
Supplemental Disclosure of Noncash Investing and Financing Information
Vesting of early exercised options	56	79
Property and equipment purchased but not yet paid	$ 40
Conversion of preferred stock to common stock upon initial public offering		8,792
Unpaid deferred costs		$ 741