Hardline Tread Doctor Knobby Cutting Tool TD-1Lightweight heated tool cuts new edges into your dull worn out knobby tires. Refresh your front or rear tire before installing a new one. Extends the life of your tire. Tread Doctor uses a specially designed heated carbide cutting blade to trim your knobby tires. This easy do it yourself tool gives you new traction for every ride! With a little practice you can cut the minimal amount of rubber off each time to get a new edge thus extending the life