Commitments and Contingent Liabilities Guarantees: Standby letters of credit were issued to lessors and insurance institutions and can only be drawn upon in the event of our failure to pay our obligations to a beneficiary. As of March 31, 2018 , we had a maximum financial exposure from unused standby letters of credit totaling $1.4 million . We are periodically required to provide performance bonds in order to conduct business with certain customers. The bonds are required to provide assurances to customers that the products and services they have purchased will be installed and/or provided properly and without damage to their facilities. We are ultimately liable for claims that may occur against the performance bonds. We had a maximum financial exposure from one performance bond totaling $0.5 million as of March 31, 2018 . We are not aware of circumstances that would require us to perform under these arrangements and believe that the resolution of any claims that might arise in the future, either individually or in the aggregate, would not materially affect our consolidated financial statements. Accordingly, no liability has been recorded as of March 31, 2018 with respect to the standby letters of credit or performance bond. We also enter into commercial letters of credit to facilitate payments to vendors and from customers. Product Warranties: We estimate product warranty liability at the time of sale based on historical repair or replacement cost trends in conjunction with the length of the warranty offered. Management refines the warranty liability periodically based on changes in historical cost trends and in certain cases where specific warranty issues become known. Changes in the product warranty accrual for the nine months ended March 31, 2018 and 2017 were as follows: Nine Months Ended March 31 (Amounts in Thousands) 2018 2017 Product Warranty Liability at the beginning of the period $ 1,992 $ 2,351 Additions to warranty accrual (including changes in estimates) 1,043 437 Settlements made (in cash or in k