This is a pack of two SWorkz 6.5mm Aluminum Lightened Wheel Hub Hexes, and are intended for use with all S350 series vehicles. These hexes have been machined to add a bit of RC bling while adding a slight weight savings. These 6.5mm hexes are the standard width. 

SWorkz also offers 5.0mm narrow lightened hexes (SWX-330506) which are ideal for the front when trying to improve steering response, but can also be used on the rear of the vehicle when reduced traction is desired.