25 pack, 4-1/2", 60 grit, x-lock, medium grit, abrasive fiber discs, designed for backing pad, fixed mount & high quality zirconia grit, snap on mounting & grinder lever wheel release, backward compatible with standard 7/8" arbor mounts, zirconia grit specially formulated with zirconia grit for speed & durability, application focused ideal for metal surface finishing, weld blending & rust removal, precision manufacturing optimized discs for less vibration & improved material removal speed.