Filter Box 17-7/8 X 21 for 16 X 20 X 1,2 or 4" Filter

Filter Box 21-3/8 X 21 for 20 X 20 X 1,2 or 4" Filter

Filter Box 24-7/8 X 21 for 20 X 24 X 1,2 or 4" Filter

Base Can 21-3/8 X 21 X 24 For RH1T4821 and RH1T6021

Base Can 17.5 in Wide Up/Downflow Furnace 18" W X 28-1/4" D X 18" H

Filter Drawer For Upflow Furnace Only Accepts 18 X 25 Filter 1,2 or 4"

Base Can 17-7/8 X 21 X 24 For RH1T2417 and RH1T3617

Base Can For 21 in Wide Up/Downflow Furnace 21.5" W X 28-1/4" D X 18" H

Filter Drawer For Upflow Furnace Only Accepts 20 X 25 Filter 1,2 or 4

20X20X35 Universal Galvanized Plenum

20X25X35 Universal Galvanized Plenum

Base Can 14in Wide Up/Downflow Furnace 14.5" W X 28-1/4" D X 18" H

Base Can 24-7/8 X 21 X 24 for RH1T6024

Filter Drawer For Upflow Furnace Only Accepts 14 X 25 Filter 1,2 or 4"