Frog Legs made my wheel chair way safer to just drive down the side walk. Instead of getting suddenly chucked out of my chair because I hit a small rock or crack in the sidewalk, the wheels would simply bounce over them. Besides being safer it makes the ride so much smoother. I first bought the 4' and loved them. Then I bought the 6" and loved them twice as much. I recommend always get the biggest widest casters you can get if you use you chair outdoors. Final note: I would will never own another chair that does not have Frog Legs on them, unless something better comes out in the future.