Used 15 sq. ft. 304 Stainless Steel Heat Exchanger. Manufactured by Perry Products. Model #4-15FTSSX. Shell: 304 Stainless Steel rated 85 psi @ 300 deg. F. Tubes: 304 Stainless Steel 35FV @ 300 F. 4" diameter x 5' tube length. (19) 5/8" od x 18 GA tubes. Heads 304L Stainless Steel. 6'4" OAL. Serial # B-4624. National Board #4244. Built 1991