The Park Tool Bottom Bracket Wrench for One-Piece Cranks is ideal for removing or tightening down some one-piece crank and bottom bracket systems. It features a double-open-ended wrench, with one side that's ideal for slotted adjusting cones with an outside diameter of 44mm or less, and a second side that is built to fit three-notched side cones that use an outside diameter between 42 and 46-millimeters.