Concentric Diffusers

Curbs Plus Concentric Diffusers are ideal for a wide range of commercial applications — from offices, retail spaces, and schools to warehouses and industrial environments.

By combining supply and return air paths into a single unit, these diffusers help reduce the need for extensive ductwork and streamline HVAC installation.

Why Choose Curbs Plus Concentric Diffusers?

✔ Built for Commercial HVAC
Constructed from G‑90 galvanized steel with durable insulation and aluminum egg‑crate return grilles, Curbs Plus Concentric Diffusers are engineered for long‑term performance in busy facilities.

✔ Fully Assembled & Ready to Install
Our diffusers come completely assembled and are designed for drop‑in ceiling installations, saving labor time and reducing install complexity on the jobsite.

✔ Multiple Styles to Fit Your Project
Choose from multiple options to fit your projects need.

✔ Engineered for Balanced Airflow
With double‑deflection diffuser cores and strategically placed inlet/outlet openings, these units help deliver smoother, more balanced airflow throughout conditioned spaces.

✔ Durable Finishes and Insulation
Each diffuser features 1″, 1‑1/2 lb duct liner insulation and is painted off‑white enamel on exposed surfaces — combining thermal performance with a clean architectural look.

CDR – Concentric Drop Box Diffuser (Round Connections)

Perfect for projects using round ductwork, the CDR model features:

  • Rugged G‑90 galvanized steel construction.

  • 1″, 1½ lb duct liner for thermal and acoustic performance.

  • Double‑deflection supply diffuser for balanced airflow.

  • Aluminum egg crate return grille for effective return air handling.

  • Off‑white enamel finish on all exposed surfaces.

  • Fully assembled for quicker installation.

  • Designed specifically for lay‑in ceiling installation.

  • Round duct connections for easy supply and return hookups.

CDR

CDS – Concentric Drop Box Diffuser (Square/Rectangle Connections)

Same performance and build quality as the CDR model, but tailored for square or rectangular duct systems:

  • G‑90 galvanized steel with full insulation.

  • Double‑deflection supply diffuser.

  • Aluminum egg crate return grille.

  • Off‑white enamel finish.

  • Fully assembled and ready for lay‑in ceiling installation.

  • Square/rectangular duct connections for flexible installations.

CFR – Flush Mount Concentric Diffuser (Round Connections)

Designed for a flush, architectural look in finished ceilings while still delivering full supply and return functionality:

  • Heavy‑duty G‑90 galvanized steel with insulated interior.

  • Aluminum louvered face grille with integrated egg crate return.

  • Fully assembled for drop‑in installation.

  • Round duct connections behind a sleek face.

  • Painted off‑white for a clean, finished appearance.

CFS – Flush Mount Concentric Diffuser (Square/Rectangle Connections)

Everything you love about the CFR flush mount — but built to connect with square and rectangular ductwork:

  • G‑90 galvanized construction with full insulation.

  • Aluminum louvered face grille with return.

  • Ready‑to‑install with no field assembly.

  • Designed specifically for square/rectangular duct connections.

  • Clean, architectural off‑white finish.

Typical Applications

Curbs Plus Concentric Diffusers are commonly used for:

  • Supply and return air distribution in commercial ceilings

  • HVAC systems with limited plenum space

  • Combined supply and return air applications

  • Offices, retail spaces, schools, and healthcare facilities

  • Drop-in installations requiring minimal components

Designed for Compact Air Distribution

Concentric Diffusers offer an efficient, space-saving solution by combining supply and return air into a single unit. Their streamlined design simplifies installation while delivering consistent airflow and comfort in demanding commercial environments.