Need help identifying some parts

[Gofaster75]

Hey guys! Bought a flux off a guy last year and he had modified the axle/wheel set up. One of the wheels fell off the other day and the wheel nut is lost in the yard. Now I need to know what this set up is called so I can get parts. All I really need is that outer nut. I've attached a few pics. Any help would be greatly appreciated!

 

[Jam Racing 1]

Looks like possibly integy hexes on that rig.....