These pictures show you the comparison between an aftermarket piston ring and an original one for Rexroth A6VM hydraulic motors. A low quality piston ring has a "crooked" breaking point - something that would've been rejected by higher quality standards. Also aftermarket rings are thinner and wear faster. They do work, though - if you reject the especially ridiculous ones from a batch, you can apply what's left and the motor will run, but these are definitely something I would never want to find in one of my hydraulic motors (if I owned one...). They only look nice till you put them next to an original Rexroth piston ring.