4-1/2" x 1/4", metal grinding, bonded abrasive wheel, x-lock arbor, type 27, 30 grit, faster, fixed mount & high-quality aluminum oxide grit, snap-on mounting & a wheel-release lever on grinder for change-out that's up to 5x faster, wheel mounts properly without the need for a spanner wrench or flange nuts, no easy to lose parts, backward compatible with standard 7/8" arbor mounts, resinoid bonds specially formulated with multiple layers of stranded fiberglass & aluminum oxide grit for speed & durability, application focused designed specifically for fast material removal with an easy-to-understand color-coding system & use with small angle grinder, precision manufacturing optimized wheels for less vibration & improved working speed.