This is a stainless steel plain back tandem roller assembly used by a variety of patio door manufacturers of metal or vinyl framed patio doors. It has an in-line tandem inner housing with 1-1/2 in. concave stainless steel ball bearing rollers set in a stamped stainless steel outer housing with rear adjustment. The housing is a plain back style that is 1-1/32 in. tall and 3/4 in. wide with a 1/4-20 threaded mounting hole on the back end and an optional use #10-32 threaded hole on the top .