Sport Semi-Metallic: High performance, low noise semi-metallic compound mounted to a steel backing plate Sport Organic: High performance, low organic compound mounted to a steel backing plate Pro: A light weight aluminum backing plate and high performance semi-metallic compound reduce weight by almost 50%, perfect for cross-country riding Pro E-Bike: friction compound developed specifically for the unique needs of pedal-assist E-bikes Extreme: An aggressive sintered compound is mounted to a vented, steel backing plate. These pads are perfect for wet conditions or downhill riding