The paint and dirt thing that everybody else says. Sound reduction is barely noticable. I did not however had a problem with the screws being different size like everybody else says. The screws that came with my Rocket Cock are the same size as the ones on the M98.
It's plastic, I'm afraid that the ring will break off. It was abused a bit and still held so I hope it keeps on holding.
It'd be better if it wasn't plastic. If you're handy enough with tools, make one yourself.