Wet shoots directly into the motor. More complicated setup. Dry shoots into the airbox. One of the good things about the infamous frame on the ZX12 is that it's part of the airbox (terrible for turbocharging) and it's easy to put a dry nitrous system on it. Drill a hole into the top of the airbox and put in the nozzle. When the nitrous is going into the airbox, the temp. sensor reads the cold from the nitrous and adds fuel. Some people put a pc on their bikes to add more fuel. I've had nitrous on my bike for 3 years now, no power commander, and it works great.