Accounts receivable, net consisted of the following:


	As of
	June 30, 2022			December 31, 2021
	(in thousands)
Accounts receivable, gross	$	38,774		$	38,426
Allowance for credit losses		(50	)		(50	)
Accounts receivable, net	$	38,724		$	38,376

Inventories consisted of the following:


	As of
	June 30, 2022		December 31, 2021
	(in thousands)
Raw materials	$	3,779	$	1,841
Work in progress		23,854		16,963
Finished goods		6,750		4,826
Total inventories	$	34,383	$	23,630

Prepaid expenses and other current assets consisted of the following:


	As of
	June 30, 2022		December 31, 2021
	(in thousands)
Prepaid expenses	$	3,923	$	2,398
Other current assets		3,458		2,078
Total prepaid expenses and other current assets	$	7,381	$	4,476

Property and equipment, net consisted of the following:


	As of
	June 30, 2022			December 31, 2021
	(in thousands)
Lab and manufacturing equipment	$	59,925		$	44,283
Computer equipment		2,392			1,977
Furniture and fixtures		463			433
Construction in progress		8,645			7,100
Leasehold improvements		5,956			5,211
		77,381			59,004
Accumulated depreciation		(25,461	)		(21,102	)
Total property and equipment, net	$	51,920		$	37,902

Depreciation expense related to property and equipment was $2.4 million and $1.4 million for the three months ended June 30, 2022 and 2021, respectively, and $4.5 million and $2.5 million for the six months ended June 30, 2022 and 2021, respectively.

Intangible assets, net consisted of the following:


	As of
	June 30, 2022							December 31, 2021
	(in thousands)
	Gross Assets		Accumulated Amortization			Net Assets		Gross Assets		Accumulated Amortization			Net Assets
Internal use software	$	9,434	$	(8,633	)	$	801	$	9,434	$	(8,633	)	$	801
Purchased intangibles		10,749		(7,247	)		3,502		11,703		(6,527	)		5,176
Intangible assets	$	20,183	$	(15,880	)	$	4,303	$	21,137	$	(15,160	)	$	5,977

Amortization expense for intangible assets was $0.4 million and $0.5 million for the three months ended June 30, 2022 and 2021, respectively, and $0.7 million and $1.0 million for the six months ended June 30, 2022 and 2021, respectively.

As of June 30, 2022, the Company had $0.8 million of intangibles that were still in development stage and were not being amortized, with the amortization beginning in July 2022 when the related product is placed in production. The estimated aggregate future amortization expense for intangible assets in development stage and subject to amortization as of June 30, 2022 is summarized as below:


	(in thousands)
2022 (remainder)	$	947
2023		1,876
2024		1,182
2025		228
2026 and beyond		70
	$	4,303

Accrued expenses and other current liabilities consisted of the following:



	As of
	June 30, 2022		December 31, 2021
	(in thousands)
Accrued payroll and related benefits	$	5,990	$	7,237
Revenue reserves		2,450		2,194
Deferred non-recurring engineering services		3,409		5,666
Short term lease liability		2,205		1,336
Accrued customer rebates		2,654		3,107
Other accrued expenses		5,290		4,742
Total accrued expenses and other current liabilities	$	21,998	$	24,282

The Company recorded reduction of research and development expenses related to non-recurring engineering service arrangements in the condensed consolidated statement of operations of $2.8 million and $0.1 million during the three months ended June 30, 2022 and 2021, respectively, and $4.8 million and $0.1 million during the six months ended June 30, 2022 and 2021, respectively.

Through June 30, 2022, the Company had recorded $2.7 million of accrued customer rebates as contra revenue under a customer agreement. In July 2022, the Company subsequently entered into an agreement with the customer to waive the accrued customer rebate through June 30, 2022. The Company will recognize this waiver as revenue in July 2022.