Intangible assets at December 31 were as follows:


December 31, 2022
Intangible Assets	Useful life	Gross Carrying Amount		Accumulated Amortization			Currency Exchange			Net
Amortized intangible assets
Patents	5-15 years	$	16,040	$	(15,437	)	$	(234	)	$	369
Developed product technology	2-10 years		169,499		(111,639	)		(6,176	)		51,684
Customer relationships	7-12 years		62,465		(42,784	)		(1,672	)		18,009
Software license and other	3-4 years		2,743		(2,677	)		(59	)		7
Total amortized intangible assets			250,747		(172,537	)		(8,141	)		70,069
Intangible assets with indefinite lives
In process research and development	Indefinite		-		-			-			-
Trademarks and trade names	Indefinite		10,303		-			(1,235	)		9,068
Total Intangible assets with indefinite lives			10,303		-			(1,235	)		9,068
Total intangible assets		$	261,050	$	(172,537	)	$	(9,376	)	$	79,137


December 31, 2021
Intangible Assets	Useful life	Gross Carrying Amount		Accumulated Amortization			Currency Exchange			Net
Amortized intangible assets
Patents	5-15 years	$	16,040	$	(15,242	)	$	(97	)	$	701
Developed product technology	2-10 years		166,819		(100,248	)		(5,736	)		60,835
Customer relationships	7-12 years		62,093		(38,760	)		(1,688	)		21,645
Software license and other	3-4 years		2,743		(2,677	)		(61	)		5
Total amortized intangible assets			247,695		(156,927	)		(7,582	)		83,186
Intangible assets with indefinite lives
In process research and development	Indefinite		2,061		-			-			2,061
Trademarks and trade names	Indefinite		10,303		-			(1,000	)		9,303
Total Intangible assets with indefinite lives			12,364		-			(1,000	)		11,364
Total intangible assets		$	260,059	$	(156,927	)	$	(8,582	)	$	94,550

Amortization expense related to intangible assets subject to amortization was $15.6 million, $16.2 million and $16.3 million for the twelve months ended December 31, 2022, 2021 and 2020, respectively. In process research and development is transferred to amortized intangible assets at the time the product becomes viable.

The weighted amortization period for intangible assets subject to amortization is 9.9 years. The schedule below sets future amortization expense of our currently owned intangible assets: