Unior Open Bottom Bracket Wrench Key Features material: premium flex plus carbon steel surface finish: chrome plated according to ISO 1456:2009 Tool also fits the disc brake rotor nuts with 16 external notches. How To Use This Tool The open bottom bracket wrench is used to remove and install ShimanoR Hollowtech II, CampagnoloR Ultra-Torque and Power Torque, Race FaceR, FSAR, SRAMR, TruvativR, Chris KingR bottom brackets as well as many and others. The 1609/2HOBBY wrench also fits on the external centerlock disc nut.