Magnetic backed diamond discs are super-fast to change and available in a wide selection to suit most grinding needs. These discs hare available with either a 1/4" hole or a 1" hole to help center it on the plate. The 1/4" models are compatible with Covington's 12" Ameritool HD and the 1" models are compatible with Covington's 12" Flat Lap Grinder.