Paintball regulators are devices designed to supply a lower pressure than in a storage vessel (A CO2 or nitrogen tank) to a paintball gun. They are used in Pneumatic cannons to step down the pressure in the CO2 tank (~800 psi) or nitrogen tank (3000-5000psi) to a usable pressure (around 100 psi). Most paintball regulators are designed for compressed air, and may be incompatible with CO2. One model which is known to be compatible with both is the Palmer Stabilizer. The "female" version will allow you to attach the tank directly to the regulator.