One of the most common issues with Roller Bumpers and Gravity Type Coordinators is that the rubber wheel dries out and eventually falls off. With this Replacement Roller For Roller Bumper, you can now just change out the wheel. The wheel has 15/16" diameter and is 7/16" wide. The hub diameter is 3/16". This package ships with the wheel and a replacement axle that features a "fast rivet" head.