HQRP Drive and Worm Gear Kit for Craftsman 13953989 13953990 13918315SR 13918415SR 13918616SR 139531006 Garage Door Opener Access System + HQRP Coaster HQRP&reg; Replacement Drive Gear and Worm Gear Kit plus HQRP&reg; Coaster; It Is Highly Recommended That You Replace Both The Drive Gear And Worm Gear At The Same Time; 100 Days Warranty!