Trail Bloc Primary clutch. JOHN DEERE GATOR RSX 850i / 860i TRAILBLOC CLUTCH. CVtech Trail Bloc Primary Clutch with HD retaining bolt, calibrations are for ATVs not UTVs. Solid upgrade over the factory unlocked primary clutch, this is a straight bolt on replacement. Locked sheaves, smaller one-way diameter and more belt grip. This is a great clutch for riders looking for a performance upgrade. This comes preset, some fine tuning may be required to get this 100% Many find these settings to be spot on. We will provide assistance in fine tuning for your riding style. Specializing in Powersports performance for over 40 years. Here at Northern Crankshafts we have been in the Power Sports Business for over 36 years. Enjoy and Safe Riding!