Quick Verdict
Both of these furnace stand return air boxes come from Ductwork For Sale. COM and are priced identically at USD 169.00. Each is hand-fabricated in Virginia from American-made 26 gauge galvanized sheet metal, with 22 gauge support rails that include a 1" hem edge for strength. They ship flat as complete kits-including foil tape, sheet metal screws, four slips, four sides, one bottom cap, and assembly instructions with a video link. Both are silver plenums, so the only real difference between them is the outside dimensions. The decision comes down to which set of measurements lines up with your existing furnace or return air opening.
Comparison Table
| Feature | 17.5" x 21" x 11" Box | 14.5" x 23" x 10" Box |
|---|---|---|
| Price | USD 169.00 | USD 169.00 |
| Outside Dimensions | 17.5" wide x 21" long x 11" tall | 14.5" wide x 23" long x 10" tall |
| Material | Galvanized Steel | Galvanized Steel |
| Thickness | 26 gauge | 26 gauge |
| Color | Silver | Silver |
| Type | Plenum | Plenum |
Where Each Box Wins
The 17.5" x 21" x 11" box is the one to pick when your opening is wider than it is long and you can spare a little extra height. The 14.5" x 23" x 10" box is the better match for spaces that run longer in one direction and where vertical clearance is tight. Both have the same construction and pricing, so the shape of your opening should decide.
Product Notes
17.5" x 21" x 11" Tall Furnace Stand Return Air Box Duct HVAC
This box from Ductwork For Sale. COM is built to match a 17.5" by 21" footprint with an 11" height. It's the wider and taller of the two options, which makes it a natural fit for return openings that are closer to square. The construction details are solid: 26 gauge galvanized steel, 22 gauge support rails with a 1" hem edge, and a complete kit that includes foil tape, sheet metal screws, four slips, four sides, and one bottom cap. Assembly instructions and a video link come with it. You get the extra vertical space inside the plenum, which can be useful when you need more room for the air transition. The only trade-off is that it won't fit into the longer, narrower footprint of its counterpart, so measure before you buy.
14.5" x 23" x 10" Tall Furnace Stand Return Air Box Duct HVAC
This is the longer option, with a 23" length that stretches 2" further than the other box. It's also 3" narrower, so it fits into tighter width openings. The build quality matches the other box exactly: 26 gauge galvanized steel, 22 gauge support rails, and a complete kit with foil tape, sheet metal screws, slips, sides, and a bottom cap. You also get assembly instructions and a video link. The lower 10" height makes it a good choice when headroom above the furnace is limited, and the longer dimension aligns with duct runs that extend in one direction. The trade-off is the reduced width and height-if your opening is more square, the other box will likely line up better.
Final Choice by Use Case
Choose the 17.5" x 21" x 11" box when your return opening is wider than it is long and you want the extra inch of internal height. Choose the 14.5" x 23" x 10" box when you need more length and have limited vertical space. Take your tape measure and match the footprint that fits.
