Industry Nine Hydra 2 Trail Carbon Wheelset - 29" 15 x 110mm/12 x 148mm 6-Bolt XD BLK 32HIndustry Nine Hydra 2 Trail Carbon Wheelset 29" 15 x 110mm 12 x 148mm 6 Bolt XD Black 32H. The Hydra 2 Trail Carbon is a do all wheelset svelte enough to compete in an XC race one day and durable enough to recover with some park laps the next. We get maximum performance out of these wheels with front and rear specific carbon layups designed to meet the different demands placed on each resulting in better ride quality at a lighter weight. 6 Pawl Hydra