Note 16. Commitments and Contingencies

(a) Lease Commitments

We lease manufacturing and office facilities and certain equipment under operating and capital leases that expire through 2037. Rental expense was $4.8 million, $4.6 million and $3.9 million under operating leases for the years ended December 31, 2019, 2018 and 2017, respectively. Future minimum lease commitments on non‑cancelable operating leases for the year ended December 31, 2019 are as follows:


	Operating
	Leases
	(in thousands)
2020	$	3,511
2021		1,838
2022		637
2023		128
2024		68
Thereafter		206
Total operating lease payments	$	6,388

(b) Sale Leaseback Financing Obligation

In addition to the lease commitments as described above, in 2015 we entered into a 22-year lease agreement relating to our corporate headquarters in Beverly, Massachusetts. The following table relates to the cash payment schedule associated with this lease obligation as of December 31, 2019:


	Lease
	Obligation
	(in thousands)
2020	$	5,720
2021		5,848
2022		5,980
2023		6,114
2024		6,252
Thereafter		79,653
Total finance lease payments	$	109,567
Less interest portion		(61,019)
Sale leaseback obligation	$	48,548

We have contracts and purchase orders for inventory and other expenditures of $62.4 million at December 31, 2019.

(d) Litigation

We are not presently a party to any litigation that we believe might have a material adverse effect on our business operations. We are, from time to time, a party to litigation that arises in the normal course of our business operations.

(e) Indemnifications

Our system sales agreements typically include provisions under which we agree to take certain actions, provide certain remedies and defend our customers against third‑party claims of intellectual property infringement under specified conditions and to indemnify customers against any damage and costs awarded in connection with such claims. We have not incurred any material costs as a result of such indemnifications and have not accrued any liabilities related to such obligations in the accompanying consolidated financial statements.