This is a twin 40mm fan mount for the Traxxas X-Maxx. It sits on the chassis brace rails securely and will not move in jumps or crashes. It allows you to upgrade the cooling for your stock motor to any 40mm fan you wish - from mild to wild. The fans screw in from the top, so any height fan will fit including the popular server fans. You can also cool your aftermarket motor efficiently with this setup!