Closed Back Carbon Arm CupsClosed Back Carbon Arm Cups: Unmatched Aero Comfort and Stability The TriRig Closed Back Carbon Arm Cups are renowned for aero comfort, providing the ultimate combination of support, stability, and performance . With a length of over 200mm and substantial arm wrap, these arm cups offer more surface area than any other production arm cups on the market. Built from durable, lightweight carbon, the Closed Back Carbon Arm Cups deliver exceptional strength