Square to Round Transition Box

(58 customer reviews)


  • Quality constructed from heavy-duty 28 gauge galvanized steel
  • Primarily for use to attach a ceiling register to your air supply
  • Can be used in many applications that transition a square duct to round duct
  • Available in a variety of common sizes, see the drop down menu for all sizes available

SKU SDB Categories ,


The FAMCO SDB square to round HVAC transition Box – diffuser is designed primarily for use to attach a ceiling register to your air supply, but can be used in many applications that transition a square duct to round duct. Quality constructed from heavy-duty 28 gauge galvanized steel. Available in a variety of common sizes, see the drop down menu for all sizes available. The FAMCO SDB square to round HVAC transition box is manufactured by FAMCO in the United States and comes with a 1-year warranty against product defects and workmanship. If you have any questions about this product, please refer to the FAQs above or feel free to contact us.

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Spec Sheet

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Square to Round Transition Box


Questions and answers of the customers

  1. A

    Yes - this is a size we are currently able to manufacture, you can select these dimensions in the dropdown.

  2. A

    Current manufacturing and shipping estimates are given in the shopping cart and at checkout.

  3. Q I need a 10"w x 3-1/4 to a "6 inch-round answer now
    Asked on May 18, 2021 5:49 pm

    This is not a size we currently manufacture, unfortunately.

  4. A

    We currently only manufacture the sizes shown in the dropdown menu

  5. Q Do you make these in 18Wx18Lx12D answer now
    Asked on April 25, 2021 1:05 pm

    Yes - all sizes available can be selected in the dropdown on the product page.

  6. A

    We currently only offer customization on volume runs with a total value greater than $5,000

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58 reviews for Square to Round Transition Box

Based on 58 reviews
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Showing 57 of 58 reviews (5 star). See all 58 reviews
  1. Chris

    Good quality

    Pretty basic square to round transition, but very well made. Ordering was easy and it got here pretty quick. The only problem was on my end, I ordered the wrong size. I needed a 12″ instead of the 14″. Oh well, I can always let my boss have them and consider it another example of the woodworkers maxim: “Measure twice. Cut once.”

  2. Christopher T. (verified owner)

    I had a question about dimension, they responded within an hour and order was made, item arrived a week later just as I had hoped. Great experience.

  3. R ALLEN (verified owner)

    The part looks nice and it was built and shipped quickly!

  4. Anonymous (verified owner)

  5. Shannon (verified owner)

    This arrived in perfect condition and fit exactly how I needed.

  6. Andrew (verified owner)

    Thanks for making these available and easy to order. Great quality. Good shipping process.

  7. Hugh Siebenthall (verified owner)

    My order was small and of little consequence to your overall operation. You followed through precisely as stated. Thank you and your entire team.

  8. Tim Thompson (verified owner)

  9. Anonymous (verified owner)

  10. john d. (verified owner)

    Quick and easy to order. Arrived in perfect condition. Good price.

  11. John B. (verified owner)

  12. tony ozark (verified owner)


  13. Roy Oldaker (verified owner)

  14. Dan (verified owner)

  15. Jose Gonzales (verified owner)

    Thank you! It was both put together and priced very well!

  16. Richard Plenert (verified owner)

  17. John Garbarino (verified owner)

    Great company ford hard to find stuff fast shipping

  18. Anonymous (verified owner)

  19. mark t. (verified owner)

    The transition box I ordered fit perfectly around my water to air heat exchanger. And very good build quality.

  20. Nick D. (verified owner)

  21. Josefa Barreiro (verified owner)

  22. Anonymous (verified owner)

  23. Josef (verified owner)

    Quality product, no problem with any phase of this order. Thanks!!!!!

  24. Kendall Marks (verified owner)

    Excellent value, fast delivery

  25. Joseph Firrantello (verified owner)

    Product was perfect for my needs. Received quickly.

  26. Anonymous (verified owner)

  27. Matthew T. (verified owner)

    Perfect!!!! Very happy!!! Will buy here again!!

  28. Hector cruz (verified owner)


  29. Andrew (verified owner)

    Great craftsmanship

  30. James G. (verified owner)

    Awesome! This has been a life saver. I bought this to help redirect heat from the furnace in my RV. It used to blow straight onto the thermostat so it never got warm inside and the furnace kept kicking on and off. Now i’ve successfully redirected all the heat and it works like it should. Haven’t burned the place down yet either!

  31. Jessica (verified owner)

  32. Glenn Fulmer (verified owner)

    Great fit and great construction.

  33. Mike M. (verified owner)

    Beautiful product, arrived quickly!

  34. Ralph P. (verified owner)

    The product was excellent quality and fit perfectly

  35. Ralph (verified owner)

    Well made u band exactly what I wanted.

  36. Bud C. (verified owner)

    As advertised, shipped promptly, very high quality product. Shipping cost was high but would buy from Famco again.

  37. Bennie Keisling (verified owner)

    Good quality & fast delivery!

  38. Ryan (verified owner)

    I put up new drywall for home renovations and in the process needed to move my return line for the a/c. The dimensions of my old return box were too large for the vent cover I needed, so I ordered a custom transition box from FAMCO. It arrived exactly as what I ordered and made the job easy to finish. And it was quite a bit cheaper than other competitors. I will definitely keep FAMCO in mind for any projects in the future.

  39. Jake M. (verified owner)

    Fast shipping and exactly what I was looking for. Came well packaged and the manufacturing was top quality. Thank you

  40. Steve Chayer (verified owner)

    Trustworthy. Have confidence in this company for delivery times and quality of product.

  41. Gregory R. (verified owner)

  42. Wayne Cox (verified owner)

    I love these people at Famco. They have never let me down. They always ship when they say they are going to ship, I highly recommend them.

  43. Armand (verified owner)

    The transition box was very well made, and arrived in a timely manner.

  44. Peter Saloufakos (verified owner)

    Fits perfect.

  45. Paul Scholer (verified owner)

  46. Bart Domingue (verified owner)

    Very satisfied

  47. Gordon Rhodes (verified owner)

  48. Loreimy Panchis (verified owner)

  49. Anonymous (verified owner)

    Custom product not found elsewhere. Exactly what I needed.

  50. Alexis B. (verified owner)

  51. Kevin K. (verified owner)

  52. Herbert West (verified owner)

  53. Charles R. (verified owner)

  54. Robert (verified owner)

    Dimensions are true as shown online. Well made. My project required a flat black finish. The FAMCO box painted up well. I primed before applying the final coat.

  55. Jim G. (verified owner)

    Well made product, worked perfectly

  56. Anonymous (verified owner)

  57. David S. (verified owner)

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