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.
31– 31 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 B31 belt is 34 inches (31+3).
Description: B31 Classical V-Belt
Length: 31 in Inside Length, 34 in Outside Length
Top Width: 21/32 in
Height: 5/16 in
Weight: 0.32 lb
Temperature Resistance: -35C to +70C
Recommended use: Agricultural and Industrial machinery
Recommended pulley diameter: More than 71mm (2-3/4")
Other specifications: Limited Oil resistant, Antistatic, Tolerance Stable
Equivalent to: 5L340, 5L-340, B31, 5L 340, B 31, B-31, Dayco BP31, BTQ-B31, B31 D&D Power Drive, Grainger 6L209