Heavy duty all metal construction Sharp blade for clean circles Side to side easy adjust measurement Simple to use - Mark center of holder, set circle radius on cutter, insert needle point on marked center and turn cutter Liftime Warranty Edward Tools Drywall Circle Cutter - 16” Diameter Cutting Tool is a durable all steel construction tool for cutting circles for heating, air conditioning, plumbing and electrical equipment. To cut a circle mark center of holder, set circle radius on cutter, insert needle point on marked center and turn cutter. Edward Tools Drywall Circle Cutter comes with a lifetime warranty.