OUR HEAVY-DUTY VENTS ARE DESIGNED TO BE WELDED INTO PLACE. EACH ONE IS CUSTOM FABRICATED, AND CAN BE CUSTOMIZED WITH LOUVERS, EXPANDED STEEL GRATING, AND DIFFERENT MATERIAL THICKNESSES.  STANDARD VENTS ARE 2" X 2" X 0.125" SQUARE TUBE AND MEASURE 12" X 12" INSIDE OPENING.  INSTALLATION AVAILABLE SEPARATE.