The BBT-18 is an updated version of the current BBT-8. The outside diameter of the tool has been changed so it provides a universal fit on all Shimano and ISIS Drive eight-notch cups.
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 centre of the casting is 22.5mm, and will not fit over the 30mm spindles.