I use these on my Losi Mini Late Model wheels and they work really great! They help prevent the wheels from catching on the walls, inside pipes, and/or other cars! I run them all the time, and one time I forgot to put them on before a qualifier. BAD IDEA!! Most all of the times I was too close to the inside pipe and touched I got turned around. The covers create a smooth surface, and the car slides right off any brushes with other objects. Granted of course that your body doesn't catch as well. It is a big difference with and without the caps though I think. They fit nice and snug in the wheel, and I just use a little flat head screw driver to pop them off. I offer them in packs of (4) "Mini Mud Covers" if anyone is interested.