This is a four roller pocket door roller assembly used on Kennaframe pocket doors and a variety of other pocket door manufacturers. The four 23/32 in. diameter nylon rollers are affixed to an adjustable spring-loaded steel bracket. They ride in a double track mounted in the top of the pocket door opening. It has a dial-adjust wheel that makes it adjustable up to 3/8 in. in height. Can be used on pocket doors 1 in. to 1-3/4 in. thick, and up to 100 lbs. each.