Bonded abrasive wheel with the X-LOCK mount design – offers a faster, fixed mount and high-quality Aluminum Oxide grit X-LOCK wheel change – features snap-on mounting and a wheel-release lever on grinder for change-out that's up to five times faster Tool-free disc swap – the wheel mounts properly without the need for a spanner wrench or flange nuts for no losable parts Backward compatible – Bosch X-LOCK abrasive wheels are backward compatible with standard 7/8 In. arbor mounts Resinoid bonds – specially formulated with multiple layers of stranded fiberglass and Aluminum Oxide grit for speed and durability