AG-2000 Front Access Housing Cut Sheet " 14 gauge cold rolled steel construction" Easily removable access grid" Contains 90 pounds of carbon (10 trays)AG-144 Carbon Housing Cut Sheet " 16 gauge cold rolled steel construction" Holds four IAQ-100 carbon panels" Built-in prefilter and final filter tracks" Contains 48 pounds of carbonAG-22 Carbon Housing Cut Sheet " 16 gauge cold rolled steel construction" Holds four AG-18 carbon elements" Contains 72 pounds of carbon