Full 2" to 7" Range (50.8 - 177.8mm). Controlled pressure assures positive, adjustable contact through full range. Operates with any electric drill. Furnished with 3" long 220 grit stones, see below for other grits. Adjustable stop collar permits quick selection of two range settings, from 2" to 4" and from 4" to 7". Stone arms are easily compressed to eliminate cylinder scratches. 23520 Replacement Stones, 220 grit 23530 Special Hard Stones, 240 grit 23540 Replacement Stones, 320 grit *Stones- SIlicone Carbide *Stones are 3/8" wide