RPM Rear A-arms for the HPI Baja 5B are designed around the stock A-arm geometry, which means they are direct fit replacements, no additional parts or accessories are needed. RPM has made a number of modifications to the arms to improve performance and durability. Key durability features are as follows: The shock mount on the lower A-arm has been moved forward to eliminate the severe rubbing issue of the wheel at the shock mount that would cause stock arms to break. By moving the shock mount forward, we were able to increase the material around the shock mount to protect the lower shock rod end, preventing it from being the lowest hanging component of the A-arm assembly. We've incorporated a third inner hinge pin boss at the inside hinge pin of the lower A-arm and tied in structural ribs that help disperse impact energy and rotational forces from engine torque over all three hinge pin bosses. Similar corner webs to those found on our front A-arms have been designed into the rear upper and lower A-arms as well to help improve strength and durability. Sold single side only. Purchase white to do your own colors as shown above - Dyed using Rit Clothing Dye Rit #43 Sunshine Orange matches Baja 5B SS chassis colors Rit #13 Purple matches Baja 5B RTR chassis colors (RPM only offers 5B A-arms in Black or White)