Variable Speed V-Belts conforming to ISO R-1604 are designated by the letter W followed by a number e.g. 16 being the belts width in mm, this is followed by a number e.g. 500 which corresponds to the pitch length Lp in mm. Belts not covered by ISO standards are designated by a set of 3 numbers e.g. 22 which denotes the belts top width, e.g. 8 which denotes the belts thickness and e.g. 1000 which denotes the belts inside length Li in mm, therefore e.g. 22×8 x 1000.