HD Clutches are designed by HD Clutch and Assembled in the USA. We use Machined Billet Pulleys for several reasons. The first, formed pulleys are damaged easily, and any 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 it opens up and allows the belt to sink in slightly, this acts like a smaller pulley and slows the belt speed, which slows downs the blades and adds additional wear to the belt. 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.