Must be installed by a licensed contractor. The RA 16 series return air drop (for upflow furnace applications only) has a built-in 16" x 25" filter rack for cold air return filtration. Equipped with "take-off" collars, this assembly allows return air to be taken from an overhead trunk line or panned floor joist to a side-return air opening of an upflow furnace application. **This product is prohibited from shipping to California.**, Lot of 1