Prime-Line Sliding Screen Door 3/4 Inch Nylon Roller Assembly 2-Pack B 629This roller is a replacement for some Croft and Keller doors. It is also found in other household situations from the closet to the bathroom. It is a ball bearing 3 4 in. high density polyethylene roller on a threaded hex hub. Often fits onto a bracket that is attached to the door while the roller rides in an upper track above the door opening.