The 23mm HD hub adaptors allow you to utilize Pro-Line exclusive 23mm HD system. It offers a wide variety of tire choices including the 40 Series Bow-Tie and the all-terrain giant MOAB; it also offers a wide variety of 40 Series wheel choices including two different offsets. Basically, if you want tune ability, then you will want to pick-up the 23mm HD hexes.

The hexes are also a bolt-on type system. Simply remove the original hex and install the new 23mm hex utilizing the original hardware. They extend the wheelbase out to the desired track width with monster truck tire.