Zipp has engineered the first thermally conductive low temperature brake pad for the bike market by working with the leading brake producer for Formula 1 race teams. Compared to traditional rubber pads Zipp Carbon / Carbon Brake Blocks are engineered for optimal performance and rim longevity under all (including extreme) conditions with both Silica-Ceramic and Aluminum braking surfaces. Compatible with aluminum braking surfaces and the Silica-ceramic surfaces of Zipp tubular rims. Highly recommended for all Zipp rims and wheelsets. Brake pads sold in packs of two pad holders to fit 10 speed Systems for Campagnolo Shimano or Sram.