The Company’s operating leases primarily include real estate leases for properties used for manufacturing, R&D activities, sales and service, and administration, as well as certain equipment leases. Some leases may include options to renew for a period of up to 5 years, while others may include options to terminate the lease. The weighted average remaining lease term of the Company’s operating leases as of December 31, 2019 was 3 years, and the weighted average discount rate used in determining the present value of future lease payments was 6.0%.

The following table provides the maturities of lease liabilities at December 31, 2019:

Minimum lease commitments at December 31, 2018 for property and equipment under operating lease agreements (exclusive of renewal options) were as follows:

Operating lease cost for the year ended December 31, 2019 was $5.5 million. Variable lease cost for the year ended December 31, 2019 was $1.7 million. Additionally, the Company has an immaterial amount of short-term leases. Lease expense was $7.2 million, $6.3 million, and $5.3 million for the years ended December 31, 2019, 2018, and 2017, respectively. In addition, the Company is obligated under such leases for certain other expenses, including real estate taxes and insurance.

On June 8, 2018, an Ultratech shareholder who received Veeco stock as part of the consideration for the Ultratech acquisition filed a purported class action complaint in the Superior Court of the State of California, County of Santa Clara, captioned Wolther v. Maheshwari et al., Case No. 18CV329690, on behalf of himself and others who purchased or acquired shares of Veeco pursuant to the registration statement and prospectus which Veeco filed with the SEC in connection with the Ultratech acquisition (the “Wolther Action”). On August 2 and August 8, 2018, two purported class action complaints substantially similar to the Wolther Action were filed on behalf of different plaintiffs in the same court as the Wolther Action. These cases have been consolidated with the Wolther Action, and a consolidated complaint was filed on December 11, 2018. The consolidated complaint seeks to recover damages and fees under Sections 11, 12, and 15 of the Securities Act of 1933 for, among other things, alleged false/misleading statements in the registration statement and prospectus relating to the Ultratech acquisition, relating primarily to the alleged failure to disclose delays in the advanced packaging business, increased MOCVD competition in China, and an intellectual property dispute. Veeco is defending this matter vigorously.

On December 21, 2018, a purported Veeco stockholder filed a derivative action in the Superior Court of the State of California, County of Santa Clara, captioned Vladimir Gusinsky Revocable Trust v. Peeler, et al., Case No. 18CV339925, on behalf of nominal defendant Veeco. The complaint seeks to assert claims for breach of fiduciary duty, waste of corporate assets, and unjust enrichment against current and former Veeco directors premised on purported misstatements and omissions in the registration statement relating to the Ultratech acquisition. Veeco is defending this matter vigorously.

The Company is involved in various other legal proceedings arising in the normal course of business. The Company does not believe that the ultimate resolution of these matters will have a material adverse effect on its consolidated financial position, results of operations, or cash flows.

The Company depends on purchases from its ten largest customers, which accounted for 67% and 61% of net accounts receivable at December 31, 2019 and 2018, respectively.

Customers who accounted for more than 10% of net accounts receivable or net sales are as follows:

*	Less than 10% of aggregate accounts receivable or net sales

The Company manufactures and sells its products to companies in different geographic locations. Refer to Note 18, “Segment Reporting and Geographic Information,” for additional information. In certain instances, the Company requires deposits from its customers for a portion of the sales price in advance of shipment and performs periodic credit evaluations on its customers. Where appropriate, the Company requires letters of credit on certain non-U.S. sales arrangements. Receivables generally are due within 30 to 90 days from the date of invoice. In some geographies, receivables may be payable up to 150 days from the date of the invoice.

Suppliers

The Company outsources certain functions to third parties, including the manufacture of several of its systems. While the Company relies on its outsourcing partners to perform their contracted functions, the Company maintains some level of internal manufacturing capability for these systems. In addition, certain of the components and sub-assemblies included in the Company’s products are obtained from a single source or a limited group of suppliers. The failure of the Company’s present outsourcing partners and suppliers to meet their contractual obligations and the Company’s inability to make alternative arrangements or resume the manufacture of these systems could have a material adverse effect on the Company’s revenues, profitability, cash flows, and relationships with its customers.

The Company had deposits with its suppliers of $5.9 million and $12.8 million at December 31, 2019 and 2018, respectively, that were included in “Prepaid expenses and other current assets” on the Consolidated Balance Sheets.

Purchase Commitments

The Company had purchase commitments of $63.3 million at December 31, 2019, substantially all of which will come due within one year. Purchase commitments are primarily for inventory used in manufacturing products and are partially offset by existing deposits with suppliers.

Bank Guarantees

The Company has bank guarantees and letters of credit issued by a financial institution on its behalf as needed. At December 31, 2019, outstanding bank guarantees and letters of credit totaled $10.2 million and unused bank guarantees and letters of credit of $21.6 million were available to be drawn upon.