Reintroducing the 2021 Profile Blackjack sprocket- celebrating 23 years since its inception! Profile Blackjack sprockets are CNC machined from 6061 Aluminum and made in the USA. The Blackjack is a "bolt on" only style sprocket and requires a sprocket bolt to be attached to crank arm. Fits 19mm, 22mm, & 24mm crank spindles: Bore size is 24mm and supplied with 19mm & 22mm adapters. For use with 1/8" chains only Specifications AdaptorIncludes adapters for 22mm and 19mm crank spindlesBore19mmBore22mmBore24mmChain Width1/8"ColorAnodized black with post production machining and laser graphicsDefined ColorBlackInterfaceBolt DriveMaterialAluminumTooth Count28