The BBT-18 is a heavy duty, investment cast tool for installing and removing the following eight-notch bottom bracket cups:

Shimano Octalink right cup with external notches

ISIS Drive

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.