Shell is rated for MAWP, 225 psi at 450 degrees F. Shell MDMT is -20 degrees F. at 225 psi. Tubes are rated for MAWP 150 psi at 450 degrees F Tubes MDMT is rated for -20 degrees F. at 150 psi Shell side inlet and outlet are 3" threaded. Tube side inlet and outlet are 2" threaded.