Traxxas 5355X Aluminum Hollow Balls Centered and Offset 

Hollow ball set, aluminum (30)/ tall centered hollow ball (2)/ tall offset hollow ball (2)/ bump steer adjustment shims; 3.5mm (2), 1.17mm (2) 

With the understanding that a gram of weight can be the difference between winning and losing a race, Traxxas hollows these steering linkage ball bearings. While reducing the weight, the hollow ball bearings maintain the original tightness in the rod ends.