10. COMMITMENTS AND CONTINGENCIES Lease Commitments. The Company leases certain office and warehouse facilities and a vehicle under noncancelable operating leases that expire at various terms through 2022 . Future minimum lease payments under non-cancelable operating leases are projected as follows: ? ? ? ? ? 2019 $ 1,064 ? 2020 893 ? 2021 648 ? 2022 405 ? Total $ 3,010 Rent expense was $1,146 , $850 and $1,250 in 2018, 2017, and 2016. Royalty Agreements. The Company has certain royalty agreements in place with terms that include payment of royalties of 3% to 5% of specified product sales. The current royalty agreements have effective dates as early as 2003 and terms ranging from eighteen years to at least twenty years. Parties to the royalty agreements have the right at any time to terminate the agreement immediately for cause. Royalty expense of $2,715 , $2,323 and $1,895 was recorded as part of cost of revenue for the years ended December 31, 2018, 2017 and 2016. Purchase Agreements. The Company enters into standard purchase agreements with certain vendors in the ordinary course of business. Outstanding commitments at December 31, 2018 were not significant. Legal. The Company may, from time to time, become a party to legal proceedings. Such matters are subject to many uncertainties and to outcomes of which the financial impacts are not predictable with assurance and that may not be known for extended periods of time. When management has assessed that a loss is probable and an amount can be reasonably estimated, the Company records a liability in the Consolidated Financial Statements. The Company received a Civil Investigative Demand (CID) from the U.S. Department of Justice (USDOJ) in December 2017 stating that it is investigating the Company to determine whether the Company has violated the False Claims Act, relating to the promotion of certain medical devices related to the treatment of atrial fibrillation for off-label use and submitted or caused to be submitted false claims to certain federal and state health care programs for medically unnecessary healthcare services related to the treatment of atrial fibrillation. The CID covers the period from January 2010 to December 2017 and requires the production of documents and answers to written interrogatories. The Company had no knowledge of the investigation prior to receipt of the CID. The Company maintains rigorous policies and procedures to promote compliance with the False Claims Act and other applicable regulatory requirements. The Company provided the USDOJ with documents and answers to the written interrogatories and is cooperating with its investigation. However, the Company cannot predict when the investigation will be resolved, the outcome of the investigation or its potential impact on the Company.