This is a K-tab patio door roller assembly with a 1-1/8 in. concave steel ball bearing roller. The T-shaped tab (K-tab) is simply slid up into a T-shaped receptacle in the bottom of the patio door. No screws are required for installation. The housing is 3/4 in. wide and 1-1/4 in. tall with a 7/8 in. dimple width. The dimples secure it within the door's bottom frame. Used by a variety of door manufacturers.