TNT Airsoft O-Ring Type Piston Kit for KWA H&K MP7 Gas Blowback Airsoft SMG (Model: Original Bolt Kit)

"There aren't really any parts on the KWA MP7 that are a must replace, it's fantastic out of the box. However the cup seal used inside the bolt is the weakest point in the system. I ruined my cup seal the first time skirmishing for a day, and have talked to others at my field who have complained about the same thing. Especially propane users, who run little to no oil in the propellent.

The TNT O-Ring piston replacement solves the issues and is a bit more forgiving when the gun is running slightly dry during a long game. The FPS is pretty dang consistent and best of all, it the o-ring piston did not raise or lower my initial FPS at all. I did not have to worry or tune anything after installing to meet my field regs. Must get part in my opinion to solve the weakness of the stock part, and get a little more accuracy out of an already accurate piece.