B/5L Section
B74/5L770 Classic V-Belt B/5L Section for Mowers Tractors Tillers B-74 5L-770
You will notice the 6 inch measurement allows for precise alignment with other 6 inch parts.
B74 or 5L770 0.656 x 77in OC Classical V-Belt for Lawn Garden Industrial Ag
A nice detail with Briggs & Stratton is the color-coded maintenance points.