A surgical stapling instrument comprises a staple cartridge assembly having a plurality of rows of staple receiving slots, an anvil assembly having an anvil member defining a plurality of rows of staple forming recesses, the staple cartridge assembly, the anvil assembly, or both, having one or more attachment members; and a staple line reinforcement material attached to the attachment members by ultrasonic welding. The staple line reinforcement material can be attached to an anvil assembly utilizing a retainer.