The Company has one operating segment, which is the sale, design, manufacture, marketing and support of optical critical dimension and thin film systems. The following tables summarize total net revenues and long-lived assets (excluding intangible assets) attributed to significant countries (in thousands):

	Three Months Ended				Six Months Ended
	June 29, 2019		June 30, 2018		June 29, 2019		June 30, 2018
Total net revenues:
United States	$	9,170	$	7,392	$	26,044	$	14,130
China		25,873		28,333		40,233		36,375
South Korea		13,070		30,980		27,038		68,798
Singapore		8,723		2,380		10,274		14,535
Japan		4,214		15,017		8,531		28,396
Taiwan		3,650		1,974		14,939		3,034
Other		2,920		2,528		7,661		5,649
Total net revenues	$	67,620	$	88,604	$	134,720	$	170,917

	June 29, 2019		December 29, 2018
Long-lived tangible assets:
United States	$	51,365	$	46,325
International		1,414		1,575
Total long-lived tangible assets	$	52,779	$	47,900

With respect to customer concentration, Micron Technology, Inc., SK hynix, and Yangtze Memory Technologies Co. Ltd. each accounted for more than 10% of total sales for the three months ended June 29, 2019, and Intel Corporation, SK hynix, and Taiwan Semiconductor Manufacturing Company Limited each accounted for more than 10% of total sales for the six months ended June 29, 2019. Intel Corporation, Samsung Electronics Co. Ltd., Toshiba Memory Corporation, and Yangtze Memory Technologies Co. Ltd. each accounted for more than 10% of total sales for the three months ended June 30, 2018. Intel Corporation, Micron Technology, Inc., Samsung Electronics Co. Ltd., SK hynix, Toshiba Memory Corporation, and Yangtze Memory Technologies Co. Ltd. each accounted for more than 10% of total sales for the six months ended June 30, 2018.

With respect to accounts receivable concentration, Micron Technology, Inc., SK hynix, and Yangtze Memory Technologies Co. Ltd. each accounted for more than 10% of total accounts receivable as of June 29, 2019. SK hynix and Toshiba Memory Corporation each accounted for more than 10% of total accounts receivable as of December 29, 2018.