NOTE 8—ACCRUED LIABILITIES

Accrued liabilities are comprised of the following (in thousands):

Changes in the initial product warranty accrual and the expenses incurred under the Company’s initial and extended warranties for the three months ended March 31, 2020 and 2019 are included within accrued liabilities on the Consolidated Balance Sheets and were as follows (in thousands):

The Company’s Waterlase laser systems sold worldwide are covered by a warranty against defects in material and workmanship for a period of up to 16 months domestically and up to 28 months internationally, from the date of sale by the Company or a distributor to the end-user. The Company’s Diode systems sold worldwide are covered by a warranty against defects in material and workmanship for a period of up to 28 months from the date of sale by the Company or a distributor to the end-user.