The HEX-FLX flywheel coupling provides operation below critical speeds with its high torsional stiffness. It minimizes spline fretting and has the best shaft clamping abilities in its class (Patent No.: US 7,645,089 B2, Jan. 12, 2010). This flywheel coupling may be blue, but don’t let it get you down. Replacing existing flywheel couplings of similar design with the HEX-FLX may even put a little $$ back in your budget.