This is a Pack of 4mm Serrated Wheel Lock Nuts for Cars and Trucks with 4mm Axles. Pro-Line wants your wheels to stay where they belong – On Your Car! Pro-Line's new 4mm Wheel Nuts feature Dual Protection against the Dreaded “Wheel Loss” found at RC tracks around the World. These Pro-Line Blue Anodized Aluminum Nuts have deep serrations that dig into the wheel and provide a secure hold against the rigors of Racing and Bashing. The second layer of protection delivered by Pro-Line's new Serrated Nuts is the Nylon Lock Ring that prevents the nuts from loosening due to vibration and centrifugal effects. Get the Security and Style afforded by Pro-Line's new 4mm Serrated Lock Nuts today!