The design modifications accommodate changes made by ARRMA for V5 and EXB versions of these vehicles, although they are reverse compatible for older models.
RPM A-arms are significantly beefier than the original 6S version A-arms. Support beams are 30% thicker, improving durability and strength while reducing flex. Less flex equates to more predictable suspension performance and handling. A second shock mount hole has been added for further outboard. This additional position provides a lower profile suspension set-up. The shocks lay down a little further, dropping the ride height for a lower center of gravity. A lower center of gravity equates to higher corner speeds.
RPM A-arms are molded from a nearly indestructible blend of engineering grade nylons for performance you can rely on when the conditions are at their worst!