Yes, they are a lot better than the stock set-ups. There are two basic ones, the R-Hop and the ER-Hop. The R-Hop is just the size of the stock barrel window, but the ER-Hop is longer and needs the window modified. The patches with the letter "I" in front of them just mean that they're more efficient in colder weather if I'm not mistaken.
If I'm wrong about anything, somebody please correct me. I'm not sure what an M-Hop is though.