Prestacycle Uniblock Pro Cassette. Features: 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 Features new ARC Technology which delivers an all-new shifting profile that provides shifting characteristics equaling or improving upon shifting performance for every major brand Compatible with Shimano drivetrains (not XD or XDR) HG10 hubs requires Prestacycle HG10 Lockring which is sold seperately Specs: Model:Uniblock Pro Freehub Type:HG10/11/12 Speed:12 Range:11-30 Cogs:11,12,13,14,15,16,17,19,21,24,27,30 Color:silver Weight:181g