ZCI Nylon Bearing Piston Head

So with the mixed reviews, I have decided to help some confusion. I recently bought 4 of these and I can say that not all of them are made the same. I did notice while 2 of them were able to take standard #14 o ring, the other 2 had a slight problem with fitting the o rings (just slightly, they still work and I feel provide a slightly better air seal). So while they are not perfect they still work. 2 still had bits of plastic that needed to be shaved off from the molding while the other 2 came out perfectly. It's your choice if you want to buy them but I would say go for it because they are similar to the guarder piston head but these seem stronger.