The MAC 57 Series is a 3-way balanced spool valve piloted by our 200 series (which means this large 3-way valve can also be ordered with the 200 series Hazardous Location version as a pilot - giving it the same standard). This is an extremely versatile valve: 1. It can be converted for use in vacuum. 2. It can be changed from a Normally Closed function to a Normally Open function by simply rotating a function plate between the pilot and the main valve 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 CL, CSA, RoHS and CE) please visit the Get Support pages on our website.