KWA M9 ptp piston head for O ring seal

Designed for a KWA M9 PTP green gas pistol. Not sure about other model pistols. I tried it on a KWA HK45 but it doesn't fit. This is an adapter to use a O-ring to seal the piston instead of relying on Elite Force's rebuild kit seal. Replaces the small aluminum piece that holds the original seal. My seal was all deteriorated and broken off. This uses a 7/16" x 1/16" O ring (10.82mm x 1.78mm) I used a green O ring but any should be fine. Nice and simple print. Now the pistol has a nice, crisp blowback action