Prestacycle UniBlock Cassettes are a single-piece unit exquisitely machined from a solid block of cold-forged Chrome Molybdenum alloy steel, then heat-treated, tumble-finished and electroplated for added durability and low-friction operation. The 2 largest cogs on the 11-40 and 11-42 HG11 cassettes are crafted with one-piece of high quality 7075 aluminum. - Single block design allows Prestacycle to remove more unnecessary material, making cassettes lightweight and easier to clean - Shifting ramps and profiled teeth provide smooth and consistent shifts - Honeycomb design allows for maximum material removal while maintaining strength - Designed to last longer than standard steel cassettes