This spring tension roller assembly is used by DorWal, Guardian as well as a variety of sliding patio door manufacturers. It has a flat tension spring, steel housing and a 1-1/4 in. high-density polyethylene roller. The roller installs into the door by snapping onto the existing diecast door frame corner. Used as top or bottom rollers. Use Prime-Line part B 514 for the 1 in. version.