A cracked or hardened piston seal bleeds off apply pressure and the clutch it feeds slips under load.10R80 10R80 PISTON KIT. This piston set restores a positive seal so the pack applies with full pressure behind it.The seals are bonded to the piston, which holds up different from a lip seal in a high cycle position. Shipping weight is 3 lb.This listing covers the 10r80 piston kit only. The parts list below is exactly what ships. Compare it against your teardown before ordering.REMCO has supplied automatic transmission parts since 1991, and every order ships with its part listing so the receiving technician can check what arrived against what was ordered. Transmission Piston Kit for 10R80 - replacement component designed for proper fit and function Designed to support proper clutch apply pressure, stroke and sealing during piston and seal work Package Includes: one transmission piston kit as described, supplied loose for piston and seal work Bonded rubber lip seals on a steel or aluminum piston body - designed for dependable service in the intended application. Ships at 3.00 lb, 18x16x5 in Intended for builders correcting apply pressure loss. Lubricate the lip seals before assembly and seat the piston square in the bore What's in the box1 x Piston Kit, 10R80Compatible vehiclesFits Mustang [17-19], Endeavour (Non-USA) [18-19], Everest (Non-USA) [18-19], Expedition [18-19], F150 1/2 Ton - Pickup [17-19], F150 Raptor [17-19], Navigator [18-19].