XCAT Launching Cart
The Launching Cart comes with 16” wheels which are better for longer distances and rough terrain.
Pneumatic tires measure 16" x 4"
I do want to note that you only really need Launching Cart if you are moving the boat over longer distances of dry ground. If you plan on assembling your XCAT on the beach near water's edge,you will probably find the boat is easy enough to just push into the water on its keels.