The must have hex sets for your XB4! Now use off the shelf wheels or even fellow racers tire sets on your XB4- with so many tire compounds you can now 'try' before you 'buy.Precision machined alloy hexes with heavy duty 2mm steel pins and setscrew to lock the hex in place. Designed to use the front B44.2 wheels on the front of your XB4. Use our 12mm XB4 hex set for the rear with rear Associated or Losi wheels.