Commitments and Contingencies Operating Leases The Company has entered into operating leases for certain office space and equipment, some of which contain renewal options. Estimated future lease payments under all non-cancelable operating leases with terms in excess of one year, including taxes and service fees, are as follows (in thousands): Operating leases Year ending December 31: 2015 $ 1,499 2016 541 2017 and thereafter 83 Total minimum lease payments $ 2,123 The above amounts include $1.1 million and $0.5 million of future minimum lease payments with respect to the Company s manufacturing facility in Largo, Florida and headquarters in Oakland, California, respectively. For operating leases that include contractual commitments for operating expenses and maintenance, estimates of such amounts are included based on current rates. Rent expense under operating leases, excluding rent relating to excess facilities previously accrued, totaled $2.3 million , $2.0 million and $2.5 million for the years ended December 31, 2014 , 2013 and 2012, respectively. Sublease rental income was immaterial for the years ended December 31, 2014 and 2013. Sublease rental income totaled $0.4 million for the year ended December 31, 2012. Performance Bonds In the normal course of operations, from time to time, the Company arranges for the issuance of various types of surety bonds, such as bid and performance bonds, which are agreements under which the surety company guarantees that the Company will perform in accordance with contractual or legal obligations. If the Company fails to perform under its obligations, the maximum potential payment under these surety bonds would have been $0.2 million as of December 31, 2014 . Purchase Commitments The Company has agreements with various contract manufacturers which include non-cancellable inventory purchase commitments. The Company s inventory purchase commitments typically allow for cancellation of orders 30 days in advance of the required inventory availability date as set by the Company a