Campagnolo 15mm Crank Bolt Spanner "Peanut Butter Wrench"

A peanut butter wrench, also known as a crank bolt spanner or a crank spanner, is a single-ended box wrench or ring spanner used in cycling to tighten older 15 mm crank bolts, or the wheel nuts (track nuts) on hubs with solid axles commonly found on track bicycles, particularly the 15 mm wrench made by Campagnolo. This is the only one-piece wrench that can be used to tighten or loosen the bolt or nut which holds the crank to a square-taper bottom bracket spindle (although a thin-walled 15 mm socket and handle will also serve), whereas any wrench/spanner of the correct size will tighten or loosen wheel nuts.