Details Tested extensively by the Dutch National BMX Team, Damien Godet, Kory Cook, and numerous other elite racers, Box Two Freewheels combine durability with lightning-fast engagement. They feature nine, super durable pawls and are available in one of three choices — 16, 17, or 18 teeth.To install, use the Park Tools FR-6 or other installation tool designed for single-speed freewheels with four notches that are approximately 32mm across measured inside to inside and 40mm outside to outside.FEATURES- 9 Pawls 108 [3.3] Points of Fast Engagement