Because studdable tires are manufactured with different tread depths, the tire studs are manufactured in different lengths that must he matched to the depth of the holes molded in the tire (see illustration below). The Stud sizes are identified by their Tire Stud Manufacture Index (FTS) number of the stud's overall length in millimeters (mm). Car Tire Studs give tires good durability. As studded tires are driven through winter, the Carbide tire studs are designed to wear at a rate similar to the tread rubber with the tungsten carbide pins wearing a little slower than the metal housings around them. This retains the stud's effectiveness to continue to chip into the ice as the tire wears. However, as with all tires, once studded tires wear down to approximately 5/32" of remaining tread depth, they will lose effectiveness in deep snow and a new set of tires should be installed if deep snow driving is still anticipated.