Understanding the Part Number
B?? The B stands for a ?B? section v-belt.?This is considered a ?Classic? v-belt style that has a top width of 21/32 (0.656) inches, but is commonly referred to as a 5/8 (0.625) inch belt. The thickness of the belt is 13/32 (0.406) inches.
57? 57 inches is the inside circumference of the belt.?For B-section v-belts, the outside circumference is found by adding 3 inches to the inside length of the belt.?So, the outside circumference of the B57 belt is 60 inches (57+3).