Price is per pair - includes 190mm brake rotors, axle spacers, #35 / 62T rear sprocket and all hardware. Air pressure should be 12 to 15 psi and never more than 20 for these tires.
Black wheels with 12mm axle size - 92mm pit bike spacing - swingarm extension required with Razors
Just like all spokes wheels they may have some wobble to them unless you get them trued.