Rhino Racing Shark Upper Arm Set (Purple) RR-1200PSHARK Upper Arms For SHARK DDSS YD2 RMX RDX RR 1200P These upper arms utilizes bearings on the pins for a more free moving and precision setup. A quick adjustment of the set screw lets you match the marks and adjust the track width. Special insert lets you tighten the arm for an even more precise feel without sacrificing the smooth and buttery movement of the bearing arm. The arm also includes a set of special spacers that let you quickly move your