It isn't custom made parts, they are mass-produced reinforcements for your TM SR-10 or for your JG BAR-10.
It was made from stainless steel. We worked a lot to reach the current size because we want to do it compatible with any of VSR hopup rubber. The newest version is totally compatible with the o-ring grooved hopup rubbers, like Modify or NineBall. It has a soft, buffer to keep the piston quiet and make it more long-lasting.