External bottom bracket tool for common Shimano Hollowtech II 44mm 16-notch interfaces which also doubles as a lock ring tool for the Priority Ace and other Priority models with a similar lock ring fixing method for rear sprockets. Unlike many bottom bracket tools on the market, the deep well socket fits over the axle and dished sprocket of the Ace to access the lock ring. A must-have tool for those who like to tinker with gear ratios, or would like to install a fixed gear sprocket. Heavy duty tool steel construction and 1/2" drive for a socket wrench.