This is an ST Racing Concepts 12mm Blue Aluminum "Lock Pin  Style" Wheel Hex Set. Using high quality CNC machined aluminum, these lock pin style aluminum wheel hex locks down on the axle pins so loosing pins are no longer a problem for your Traxxas electric Stampede, Rustler, Bandit and Slash, as well as the Nitro Slash. Aluminum hex are also more durable and less likely to strip out and provides a better fit to the wheel hex.