The wheel diameter is 1 1/8". Assembly is 2 1/8" long side, 1" tall and 1/2" wide.
Marking on side is A S and 81 3. It might have a 9 between the 1 and 3.


It's tough to say for sure. What you're showing us just the inside portion of a roller unit. The outer housing is missing, perhaps still installed in the door. That said, see our 81-007. This was used on Capitol and Remington patio glass doors. I think this could be the one you need. The A-S stands for Allen Stevens, who is no longer in business.