This is an optional Vaterra Aluminum Wheel Hex Set, and is intended for use with the Vaterra Kemora and Kalahari 1/14 scale vehicles. These aluminum hexes use an o-ring to secure the cross pin, and will help to prevent the hex from coming off when you remove the wheel, helping to improve reliability, as well as increase rigidity when compared to the stock plastic parts. Package includes four wheel hexes, four o-rings and four cross pins.