Professional grinding wheels for Silvey and Simington chisel chain grinders. These wheels are 8" in diameter and 3/16" thick. Wheels are made of vitrified aluminum oxide and are very fine grit compared to other grinding wheels. This means they leave an unbelievable edge, but you cannot remove material quickly without burning the cutter. They must be dressed with a diamond before use. Gray wheel is what comes stock on Silvey grinders. It leaves a very fine finish, but will loose shape faster than white and salmon colored wheels.