they stop your frame from flexing outwards when you brake (if you want to see this go run outside/or where-ever your bike is, and look at the rear maggy and pull the lever like a beast and you'll see the frame bend outwards slightly) so you brake feel stiffer and is stronger because of it, it also protects your crossover and looks pimp! you install them by removing your bolts from the mounts then putting the longer bolts back in with the booster and spacer on as well it's prety obvious what you've got to do, it's just fiddly