the axle threads are m4, the hex area is 5mm
same as almost any other truck axle Brian
there are 14mm hubs, and 12-14mm, and 12-17mm adapters available if you don't like the common 12mm
Just remember, a adapter usually widens an axle except there is a 12-14mm one on Junfac.com that just increases it 3-4mm each side