When its time to replace your Shimano Octalink bottom bracket, reach for the Park Tool BBT-18 Bottom Bracket Tool to make the job a breeze. It uses its eight pins to lock into place, each with a width of 3. 9mm. The internal hole in the tool is 22. 5mm, so it will not work on bottom brackets with a 30mm shell. It's ideal for ISIS Drive and Shimano Octalink right cup bottom brackets with external notches.