Unused 4611 Sq ft 304 Stainless Steel shell and tueb heat exchanger. Manufactured by PX Engineering. CS Shell rated 150 PSI@200F> (668) 304 SS .625"OD U-Tubes rated 75PSI@212F. 304 SS Heads. (2) Saddle mounted. Serial #556-B1. National Board #704. Built 1980.