Our AAMA window sticker shows the following:
Code: MI-1
Spec: HS-B2
Series: 420
MST: 9154
The sample picture shows two rollers, most of the windows have only one under each side (meaning that this sample wasn't pulled apart when installed). The "railing" off the left side goes over a railing on the window. Overall it is 3/4" wide (including the rail hook); each one is 7/8" (or 1 7/8" together); 5/16" high.