The MAC 55 Series is a 3-way balanced spool valve piloted by a small direct operated balanced poppet valve. This is an extremely versatile valve: 1. It can be converted for use in vacuum. 2. It can be changed from an Internal Pilot to an External Pilot function by simply rotating the adaptor between the pilot and valve main bodies. 3. It can also be converted to a remote air operated valve by removing the solenoid pilot assembly - just to name a few. For information regarding certifications (such as UL, CSA, RoHS and CE) please visit the Get Support pages on our website.