N 6686 is a 1-3/16 in concave steel ball bearing roller assembly that installs into a 1/2 in deep by 2-15/16 in long mortised pocket on each end of the solid wood closet door bottom rail. The roller assembly is held in place by two 3/4 in long screws. The bracket is stamped steel with a 1-3/16 in steel grooved ball bearing roller installed. Rides on a metal track installed onto the floor. Used by several manufacturers of solid wood closet doors.