G&P 870 Piston O-Ring Version

Someone requested it so I gave it a shot. This is a potential o-ring version piston for the G&P M870 airsoft shotguns and other clones. The design is based off a APS2 piston that takes o-rings as they are the same diameter and the piston heads from the APS2 work in the M870s. I haven't printed it so I have no idea if or how well it works but its pretty simple and uses the same base as the original so I assume it will be good to go. The o-ring size that you will need is a 20mm x 13mm x 3.5, you c