This spacer measures 7-3/4" in length, 4-1/2" in width, and is 1/2" thick. It is nonmagnetic. Spacers are used in the press to lessen the amount of effort needed to extend the jack and activate the items being used in the press. Top and bottom platens are not meant to touch - it will cause the jack to overextend and cause leaking, or for jack to fail. Always use spacers on lower platen to take up space between platens.