What is the Shimano TL-FC16 crankset arm tool for?

The TL-FC16 is Shimano's crankset arm installation tool for Hollowtech II left crankarm installation. The left crank arm on Hollowtech II cranksets is secured with two pinch bolts rather than a traditional crank bolt -- the TL-FC16 engages the preload adjustment cap on the left arm and is used to set the correct bearing preload before tightening the pinch bolts. Using this tool ensures proper bearing preload, prevents play in the bottom bracket, and avoids overtightening that can damage the bearing system. An essential tool for any Hollowtech II crankset installation or service.

Compatible with Shimano Hollowtech II cranksets across road and MTB groupsets. Typically used in combination with a 5mm hex key for the pinch bolts.