Prime-Line Products B 514 Screen Door Tension Spring with 1-Inch Nylon Roller,(Pack of 2) 1in. O.D. nylon center grooved roller Heat treated high tension steel spring Roller installs into door by snapping onto existing die cast door frame corner Height adjustment is made from edge of door by turning screw in corner 1in. O.D. nylon center grooved roller Roller installs into door by snapping onto existing die cast door frame corner Height adjustment is made from edge of door by turning screw in corner