Intangible Assets

Intangible assets consist of the following (in thousands):



	Useful Life in Years	June 30, 2018			December 31, 2017
Trade name	15 - 20	$	1,208		$	1,208
Patents and know-how	5 - 12	4,113			4,113
Customer relationships	4 - 8	730			750
		6,051			6,071
Less accumulated amortization		(5,081		)	(5,020		)
		$	970		$	1,051

The Company recorded amortization expense related to amortizable intangible assets of less than $0.1 million and $0.1 million during the three months ended June 30, 2018 and 2017, respectively and approximately $0.1 million and $0.2 million for the six months ended June 30, 2018 and 2017, respectively

Estimated amortization expense for each of the next five years is as follows (in thousands):



Years ending December 31:
Remainder of 2018	$	81
2019	162
2020	162
2021	162
2022	142
Thereafter	261
	$	970