High quality piston seals for Hatsan 125 airguns in all mods. Opened type and closed type. Opened type is better for using with gas pistons. Closed type is better for using with standart coil springs, because of less piston rebound. But this is not strict rule.Made of polyurethane by famous russian tuning specialist Vado123. Diameter - 29 mmHeight (opened type) - 6 mmHeight (closed type) - 8 mmWeight - 1 gResourse - 2000-5000 shots (depends on cylinder surface) Lot is 2 pieces.
For easier installation of opened seal you may hold it in the hot (70-85 C degrees) water for 10 seconds before it. 
Don't cut the seal by cylinder sharp edges: use the mounting blade or smooth screwdriver (look at the photo)