HD Clutches are designed by HD Clutch and Assembled in the USA. We use Machined Billet Pulleys for several reasons. The first, it is easy to damage formed pulley and damage (even a small stone nick) damages the belt with every rotation. With our Billet Pulley design we include a snap ring so the bearing is replaceable, making this clutch rebuildable. Lastly and most importantly, a Billet Pulley does not spread during tough loads and maintains a Constant blade speed. Allow us to explain: When a pulley spreads the belt sinks in slightly and this acts like a smaller pulley and slows the belt speed down. It's not much but it also wears the belt more. Higher Torque: We add a few more windings to our coils to provide the maximum gripping strength to prevent damaging micro-slipping. Clutches all run very hot; we use a composite material instead of plastic to allow the heat to dissipate much faster. This makes the HD Clutch run much cooler; extending the bearing and clutch life. HD Clutch wrote the Bearing specifications to include Premium C3 Rated Bearings and high temperature rated synthetic grease to combat heat. Less Heat = Extended Life.