I am now making tools for the dirt oval racers that use Cooper's or Custom works foam the tool was design to put the radial groove it foam tires. The tools come in a set. one for the front and one for the rear. The tool has teeth machined for it to cut the foam. How the tool works is the tire rotates in the tire lathe. you hold the tool above the center of the wheel. The cutting edge angle downward and you gently press the tool into the tire. The cutting depth is 3/16 deep. I also have the special cutter that has the correct diameter for cutting tracten bar in the foam tire. you can see picture of the product at www.speedysracingparts.com