The BBT-18 is a heavy duty, investment cast tool for installing and removing the following: Shimano® Octalink® right side bottom bracket cup with external notches Bontrager® ISIS Drive™ bottom bracket cups Front chainring lockring for Bosch® Gen 3 and Gen 4 e-bike systems FEATURES: The BBT-18 has 8 notches with an outside diameter of nominally 43.4mm. The inside-to-inside width is approximately 38mm. Each notch is approximately 3.9mm wide. The hole in the center of the casting is 22.5mm, and will not fit over the 30mm spindles. Can be used with a 36mm socket or open-ended wrench.