Fits model T/T-100 that uses the thin/narrow belt. Tumbler Belts. This belt is 1/8" thick. The other option is 1/4" thick. Take a look at the pictures for your belt width. They not only far exceed the OEM specs but also exceed any other belt you can buy.
Excellent belts that fit perfectly on my Thumler's Model T. Time will tell, but initial quality and the likelihood of longevity seem higher than the OEM belt.