Afew years ago my Warrior ran short of energy, on taking out piston the seal had broken up. Being in the car garage repair business i had loads of old and recent brake cylinder repair kits on my shelf it took me acouple of minutes to find approx rite size. It works ok the pistol now has a decent amount of performance. If brake seals are good enough for your braking effort on a car they are good enough as a piston seal in a air gun. Problem now is can you source any from car spare shops etc. Roly.