Gates K050400RB Blue Racing Micro-V Belt Belts are precision ground, not cut, so they fit the pulley with absolute perfection 5 Ribs, .667 inch (17mm) top width, 40'' (1016mm) effective length, 40.57'' (1030mm) outside circumference High-modulus, low-stretch polyester means Herculean strength for high load-carrying capability Aramid reinforcement in a patented EPDM compound for three times the heat resistance and durability of standard belts Patented EPDM compound gives Gates Racing belts extended service life