This is a pack of four optional Pro-Line 4mm Serrated Wheel Lock Nuts, and are intended for use with vehicles with 4mm axles. 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 these Pro-Line serrated nuts is the nylon lock ring that prevents the nuts from loosening due to vibration and centrifugal effects. 
Features:
 
Blue Anodized Aluminum – Stylish and Lightweight
Serrations that dig into the wheel for security
Nylon lock nut for second layer of wheel nut security