Includes: Installation Instructions, 4 Air Tires, 4 Axle Extensions, 1 Locking Hub and Installation Hardware. Our axle extensions attach with three set screws. Therefore with our kit there are more points of attachment to the axle. Our locking hub has eight points of engagement for the lock. Therefore with our kit there is less rotation of the wheel to get a locking position. Our wheels are secured with a cotter pin. Therefore with our kit the wheel is attached more securely with a cotter pin than a push nut which over time could pop off.