Wideners designed to go over factory 7mm hex on micro rc vehicles in order to widen wheel stance. They are designed to go over hex so that they do not get damaged by axle pin. Barrel nut/ sleeve nuts not provided in this listing and will be necessary for instalation. Standoffs can be used in place of barrel nuts if hex inner hole is carefully drilled to match standoff diameter, or standoff is ground down to match. These wideners are stackable as well if increassed width is needed. Each widener will add 4mm or 7mm of extra width.