The steel plate is a precisly machined perfectly round, flat, smooth disc that is attached to the potter’s wheel with special bat pins which are included. It is used as a base to firmly attach and easily remove the magnetic backed grinding and smoothing discs as needed. The flat steel surface has no irregularities that would be transfered to the grinding discs, resulting in a smooth, "bumpless" long lasting effective removal of hard ceramic material. The steel plate has 2 holes 10.0” apart and is held in place by the bat pins just like a throwing bat. The plate is designed to be heavy enough to give stability to the grinding operations and light enough to avoid stress to your potter’s wheels. It is manufactured in California.