The Faithfull aluminium oxide vitrified grinding wheels are suitable for use on most types of bench grinders and are suitabel for normal grinding of ferrous metals. Supplied with bore reducing bushes and will fit bench grinders with the following shaft sizes: Centre bore size 19.05mm, supplied with 12.7mm reducing bush.Wheel Size: 150mm x 20mm x 31.75mmGrit: 60Bond Hardness: NM/S: 35Max R.P.M: 4,500