The following table summarizes the Company’s principal contractual commitments, excluding operating leases, as of June 30, 2021 (in thousands):

	Purchase Commitments		Other Contractual Commitments		Total
2021 (remaining six months)	$	22,950	$	227	$	23,177
2022		8,698		—		8,698
2023		112		—		112
Total	$	31,760	$	227	$	31,987

Purchase commitments for inventories are highly dependent upon forecasts of customer demand. Due to the uncertainty in demand from its customers, the Company may have to change, reschedule, or cancel purchases or purchase orders from its suppliers. These changes may lead to vendor cancellation charges on these purchases or contractual commitments.

The following table summarizes the Company’s warranty accrual account activity during the three and six months ended June 30, 2021 and 2020:

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021			2020
Balance at beginning of period	$	335	$	386	$	321		$	407
Accruals for warranties charged to expense		17		15		33			24
Cost of warranty claims		—		—		(2	)		(30	)
Balance at end of period	$	352	$	401	$	352		$	401

The Company provides warranties on certain product sales for periods ranging from 12 to 36 months, and allowances for estimated warranty costs are recorded during the period of sale. The determination of such allowances requires the Company to make estimates of product return rates and expected costs to repair or to replace the products under warranty. The Company currently establishes warranty reserves based on historical warranty costs for each product line combined with liability estimates based on the prior 12 months’ sales activities. If actual return rates and/or repair and replacement costs differ significantly from the Company’s estimates, adjustments to recognize additional cost of sales may be required in future periods. Historically the warranty accrual and the expense amounts have been immaterial.