Park Tool double-ended cone wrenches are designed for the home mechanic or occasional user. Made of thin steel and are nickel plated and heat treated for long use. Available in four popular sizes from 13mm to 18mm. Their small size makes them ideal to carry along for quick repairs. The Cone is a fire testing tool based on the principle that the amount of heat released from a burning sample is directly related to the amount of oxygen consumed during the combustion. Features: These cone wrenches are designed for the home mechanic or occasional user. They&';re made of thin steel and are nickel plated and heat treated for long use. Their small size makes them ideal to carry along for quick repairs. Available in four popular sizes from 13mm to 18mm. Park Tool PT-03 Double-Ended Bicycle Cone Wrench