I ordered these to replace the really cheap casters that used to roll the bed in my camper van when the slide was extended. The second photo shows one of the old wheels that I replaced with a new one next to it. It's about 1/4 inch taller than the old wheel, but that's not a problem. Four screw holes are best for general use. For my setup it was better to drill two more holes in the middle of each wheel. End for an easier installation I recommend these wheels.