Pocket Door Roller has tricycle hanger unique 3 nylon wheels to ensure all wheels carry door weight equally. Smooth rolling balanced wheels offer minimum friction riding on a convex track rails.
"Flip-of-a-clip Metal not plastic" separates wheels from hanger plate for easy door installation/removal. 
For doors weighing up to 80 lbs.
 It includes a steel mount for an accurate and stable fit. This sliding door roller measures 1" in length and offers smooth opening.  Screws not included.

See print picture.
Wheel diameter: 3/4"
Top steel mount bracket:  2 1/4" long x 3/4" wide
Length: 2.25"
Height: 1.44" - 1.94"  adjust the nut 
Width: 1"
Product Type: 111 Series Door Hanger 1020

Please let me know if you have any questions.
Thank you,
Babette