Priced each, sold each

Sliding Glass Door Roller Assembly 1-1/2 in. nylon ball bearing roller, adjustable steel housing
Used by several patio door manufacturers.

Also used on Closet Doors

Diameter: 1-1/2-inch
Housing Tab Style: F-Tab
Housing Width: 5/8-inch
Material: Nylon
Roller Diameter: 1-1/2-inch
Roller Edge Type: Concave
Roller Material: Nylon
Type: Concave
Width: 5/8-inch

Helpful Article: How to Replace Rollers in an Aluminum Sliding Glass Door