Bought and put this piston in my Echo 1 G36C. I don't regret it.
Been installed for two months now, still without wear after around 5K rounds and an M110. Stock O-Ring was too small to provide decent compression, and I replaced it with the stock JG O-Ring (for some reason the JG o-ring provided better compression than a #14 size). Compression is now very good, but not perfect.
Bearings do their job and also add 10 or so FPS because they are like a spacer, and add a little extra tension to the spring. Porting is pretty good, and their are several around the head, in a weird teardrop-like shape. They serve their purpose well though.
Also, this is the stock piston head for the G&G Soc 16, which I have heard great things about.
Price vs. Quality ratio (low price:high quality)
Bearings relieve spring tension
Bearings act as a spacer and provide ~10 FPS boost
O-Ring too small (almost all piston heads have this problem, both pre-installed and after market ones)
Great piston, definitely recommended.
Rating: [5 of 5 Stars!]