ZCI Lightweight Nylon Piston Head

Worked very well at first, providing a great air seal.

However, after a while the o-ring that was included must have shrank because it won't seal well at all..this wouldn't be an issue except for the fact that most o-rings do not fit in the piston head groove-it is much smaller than most. I'm sure you could do some sanding but I just swapped it and threw it in my parts bin.

Seems to be made well.