It is Gas Nitrogen and it is about 750 PSI pressure. Don't mess with it yourself. It requires special tools to re-fill. Suspension shop like Racetech can handle this for you.
I HAVE A 2006 KAWASAKI NINJA ZX6R AND THE SHOCK THAT SITS UNDER THE DRIVER NEEDS TO BE FILLED UP. SOMEBODY TOLD ME THAT IT MIGHT NOT TAKE REGULAR AIR. CAN ANYBODY HELP ME WITH THIS?