Most motorcycle tires utilize some standard of measurement to quantify the durability and strength of the tire. Kings Tires use a ply rating and/or a load and speed rating. The ply rating consists of a number (usually 2, 4 or 6) followed by the letters PR. This rating indicates that a given tire has a carcass roughly as tough as a 2, 4 or 6 ply tire, as indicated by the rating. Ply rating and actual ply number do not necessarily correspond. The speed and load rating consist of a 2-digit number, followed by a single letter, e.g. 49M. The 2-digit number is the load rating of the tire. To the right is a chart showing the actual load, or weight, a given tire is capable of carrying safely, as indicated by the load rating. The letter indicates the speed rating. Again, at right is a chart indicating the correlation between the speed rating, and how fast the tire may safely be driven.