A-arms for the Associated B64 & B64D were designed to solve the amount of slop at the hinge-pins can cause your suspension settings to wander (we found as much as 0.003" or .076mm of clearance in the hinge pin holes of a stock set of new A-arms). RPM's hinge-pin holes are held to extremely strict tolerances, with no more than 0.0005" to 0.001" (.013 to .025mm) of clearance, an improvement of nearly 300%!