This powder coated steel rack adaptor mounts to the center fork crown hole on your steel or aluminum fork (or carbon fork if the manufacturer allows it) and gives you two fork crown mounting points for our rack struts. The adaptor is drilled for an M5 bolt for the fork crown, and includes an M5x45mm bolt (you may need a longer or shorter bolt depending on the thickness of your fork crown) and M5x16mm bolts for attaching our rack struts to the adaptor, as well as nylock nuts and washers.