This rubber grommet is designed to help isolate vibration in a bolted assembly. The 1/2" thick bushing measures 1 inch OD and accepts a 5/16" (8mm) bolt. The rubber is fairly hard and does not compress easily, so it can support relatively heavy items without collapsing. Note that this grommet will not isolate the item electrically. This is the same grommet supplied with all of our karting air intake and exhaust pipe cradle assemblies.