This is an Italian made axle and is used by some European kart manufacturers as their OEM axle. The inboard sprocket location has an inner reinforcement sleeve for shifter applications.
Wheel hub- 2 peg(6mm) with 30mm spacing (#K485)
Outboard sprocket hub- 2 peg(6mm) with 30mm spacing (#K485)
Brake hub and inner sprocket hub key - 3 peg(7.5mm) with 15mm spacing(#K959)
Generally speaking a harder(stiffer) axle will transfer weight faster and increase rear grip. A softer(more flex) axle will transfer weight more slowly and decrease rear grip.