Why does the new BoXXer have 38mm upper tubes? We wanted to create the best downhill fork on the market, looking at all aspects of the system. We found that the 38mm chassis provided the best balance of stiffness and performance. Related articles What is the range of adjustability on Charger 3 RC2? Why are there lines on BoXXer’s upper tubes? Does BoXXer feature PRV’s? What are the features of BoXXer’s new crowns? What is Vivid’s maximum air pressure?