The two stage self-driven pressure regulators series FB are widely used both in civil end industrial installations using Natural gas, LPG or not corrosive gases. These regulators have been conceived to be directly installed on user’s flow meter or assembled on riser shafts for civil uses. They can be installed in any position provided that they are protected against atmospheric agents. The internal relief valve vent can be convoyed outside in case of installation with closed rooms or for underground plants. Thanks to the concept of double regulation stage, it is possible to achieve a: high accuracy; high operating reliability. Simple installation procedure. The regulator are manufactured according to UNI 8827.