Acquired identifiable intangible assets, and related accumulated amortization, as of December 31, 2021 and 2020 consist of:

	December 31, 2021
	Gross Carrying Value			Accumulated Amortization			Net Book Value
	(in thousands)
Customer relationships	$	8,355		$	6,315		$	2,040
Tradenames		3,066			730			2,336
Developed technology		1,884			440			1,444
Foreign currency		(896	)		(865	)		(32	)
Total Intangible Assets	$	12,409		$	6,620		$	5,788

	December 31, 2020
	Gross Carrying Value			Accumulated Amortization			Net Book Value
	(in thousands)
Customer relationships	$	7,915		$	5,584		$	2,331
Tradenames		2,686			425			2,261
Developed technology		784			177			607
Foreign currency		(845	)		(784	)		(61	)
Total Intangible Assets	$	10,540		$	5,402		$	5,138

In connection with the October 2012 acquisition of TB Europe, the acquired intangible asset related to customer relationships is being amortized over an estimated useful life of thirteen years with the amortization being included within sales and marketing expense.

In May 2019, the Company completed its acquisition of the business and assets of ROCCAT. The acquired intangible assets relating to developed technology, customer relationships, and trade name are subject to amortization. In January 2021, the Company completed its acquisition of the business and assets relating to the Neat Microphones business. The acquired intangible assets relating to developed technology, customer relationships, and trade name are subject to amortization. Refer to Note 2, “Acquisitions” for additional information related to ROCCAT’s and Neat Microphone’s identifiable intangible assets.

Amortization expense related to definite lived intangible assets was $1.3 million, $0.9 million and $0.6 million for the years ended December 31, 2021, 2020 and 2019, respectively.

As of December 31, 2021, estimated annual amortization expense related to definite lived intangible assets in future periods is as follows:

	(in thousands)
2022	$	1,281
2023		1,041
2024		1,008
2025		889
2026		637
Thereafter		964
Total	$	5,820

All goodwill is attributable to the gaming accessories reporting unit. Changes in the carrying values of goodwill for twelve months ended December 31, 2021 are as follows:

	(in thousands)
Balance as of January 1, 2021	$	8,178
NEAT Microphones acquisition		2,508
Balance as of December 31, 2021	$	10,686