Specifications for Belt Size 399-3M-12 Cross References Numbers: 399-3M,  399-3M-12,  399-3M/12 Number of Teeth 133 *Length of Belt 399mm or ~15-11/16" Peak to Peak Distance Between Two Adjacent Belt Teeth 3mm or ~1/8" Width of Belt 12mm or ~7/16"

*Length of belt is the overall size of the belt's loop measured as if the belt were cut between two adjacent teeth and laid out on a flat surface.