Magnetic backed diamond discs are super-fast to change and available in a wide selection to suit most smoothing and pre-polishing needs. Resin bond discs are great for pre-polishing your glass and stones. The resin that holds the diamond in place uses a more relaxed bond which is perfect for pre-polishing. These discs have a 1" hole to help center on your steel plate. Use in combination with Covington's 12", 18" or 24" Flat Lap Grinder for optimum performance. Available in 12", 18", and 24" sizes.