Tom,
Tractor Supply sells the belts based on the actual size and length of the belt. Our store has the belt gauge hanging by the belts, and using that with the A/C belt that was too small (narrow) [and ending up being too long once it was on the pulleys] allowed me to select 2 belts that were possibilities. Brought them home and tried them, keeping them clean, and found one of my selections to be just right, and then took the other one back and got a duplicate of the one that fit to keep as a spare. Really, when changing belt gauge (width) from whatever is on there already, it is a trial and error process. The belt gauge in the store and some intelligent thinking reduced the error part down to 1 belt that did not fit (too short) and the next size up (in inches) that fit just right and did not have to be stretched so tight as to cause the back of the belt to be concave. It is indeed a lawn mower drive belt, but it is tough, good for any RPM the the 455 will turn, and does not slip when the A/C clutch engages, like the "proper" belt from the NAPA store did. You will not be able to look it up at the store, it is strictly a do it yourself operation...but it works very well!