Discontinued. 

Sold each, priced each

1-1/2 inch steel ball bearing roller
Adjustable steel housing assembly
Used by Crown Windows and other glass door manufacturers
Housing dimensions: thickness, 3/4 inch; length, 2-3/4 inch; height, 1-9/16 inch; overall thickness, 7/8 inch.

Diameter: 1-1/2-inch
Housing Tab Style: Plain Back
Housing Width: 3/4-inch
Material: Steel
Roller Diameter: 1-1/2-inch
Roller Edge Type: Concave
Roller Material: Steel
Type: Concave
Width: 3/4-inch

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