Mr. Tuffy liners are extruded plastic between 1 and 2mm thick whose thickness varies with the type of tire and its width, that it will be used in. They are thickest at the center, tapering to a feathered edge at the sides. The original Mr. Tuffy liner has now been superseded by "Mr. Tuffy The Next Generation" which have a second Black plastic lamination on the tire facing side, is affixed permanently to the liner, and feathers smoothly into its surface. The Black laminate is made from a harder and more "slippery" plastic which helps prevent tube punctures by barring or deflecting penetration.  Each size accommodates a specific tire diameter with a range of widths, and each size is made in a different colour.