Can be retro-fitted to all Primo belt drives with a diaphragm spring. This BDL kit replaces the pressure plate and diaphragm but uses the Primo retainer and bolts. Patent pending internal lock-up clutch design from BDL. Works with steel balls that apply pressure under centrifugal forces. Amongst others all BDL 2" Signature Series belt drive kits come equipped with this clutch. Note: Fits all Primo belt drives with diaphragm spring operated clutch. This BDL kit replaces the pressure plate and diaphragm but uses the Primo retainer and bolts.