Cal-Van Tools Sub Compact Brake Cylinder Hone is recommended for cylinder bores 1/2 inch to 2-1/4 inch (13 millimeter - 57 millimeter) diameters. It offers fast easy cutting with high or low speed drills. It is self aligning and self centering. It has a flex joint drive with adjustable tension. It includes: two(2) 1-1/8 inch (29 millimeter) medium grit stones and replacement stones: no.763 1-1/8 inch (29 millimeter), medium grit, 220-240 grit.