Compact and portable chain tool with 7 function full metal folding tool that slides into your MTB bottom bracket for easy access The built-in magnets secure and hold the folding tool in place. For those who like to ride without a bag or pack, this stealthy multi-tool is a great choice. Compatible with SRAM® DUB cranks and, Shimano® GRX / Deore XT / SLX cranks, and FSA Hollow cranks. Cranks need to have a hollow spindle that is at least 124mm wide with an internal diameter of between 19-25mm to allow the tool to fit.