CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Income Statement [Abstract]
Net sales	$ 32,583	$ 27,093
Cost of sales	8,403	7,662
Gross profit	24,180	19,431
Selling, general and administrative expenses:
General and administrative	6,837	5,771
Marketing and selling	10,143	7,454
Research and development	5,635	5,407
Total selling, general and administrative expenses	22,615	18,632
Operating income	1,565	799
Other income (expense), net:
Interest income (expense), net	271	(12)
Loss on foreign currency transactions	(248)	(77)
Royalty income	171	157
Other income, net	97	17
Total other income, net	291	85
Income before income taxes	1,856	884
Provision for income taxes	489	301
Net income	$ 1,367	$ 583
Net income per share:
Basic	$ 0.03	$ 0.01
Diluted	$ 0.03	$ 0.01
Weighted average shares outstanding:
Basic	44,235	41,410
Diluted	46,913	43,087