Grinding stones for chain saw chain sharpening, 3 pcs. Grinding stones are ideal for sharpening chainsaw chains, knives, garden tools, etc. Grinding stones: 1x 4 mm (5/32"), 1 x 4.5 mm (3/16") and 1 x 5.5 mm (7/32"). Spindle shaft diameter: 3.2 mm. Working diameter: 4- 5.5mm Max RPM: 35000rpm Package Contents: 3pcs Compatible with any multi-tool that has a 3.2mm collet, such as Ryobi, Dremel and other brands.