The Problem Solvers Sheldon Fender Nuts are an awesome way to avoid the brake-centering problems caused by mounting fenders directly to your brakes. They're named after the inventor and bike guru, Sheldon Brown. These special Sheldon nuts take the place of your existing brake nuts. They have threaded extensions for standard 6mm bolts (sold separately) providing a secure mounting place for your fenders that won't mess with your brake adjustment. They make it easier/faster to install and remove fenders, too, so they're great for commuting bicycles.