HOW TO MEASURE - Always measure the neck size to determine which size you should order. Neck Size = Listed Size. If the neck size is 8" please order 8" size option. Outer diameter of diffuser is larger. Handua steel round air supply diffuser is designed for ceiling applications. HIGH-QUALITY MATERIALS - Crafted from heavy-duty steel, this round diffuser vent ensures robustness and long-lasting performance. Its sturdy construction ensures long-term durability, making it a reliable choice for both residential and commercial applications. EFFICIENT AIR DISTRIBUTION - The round vent cover incorporates concentric rings strategically designed to deflect the air in a 360-degree pattern, effectively enhancing air circulation. Using our round HVAC ceiling diffuser within your ventilation system will improve your home circulation. The round ceiling diffuser offers precise sizing for optimal air distribution. Additionally, included butterfly damper provide more functionality and control. ENHANCE HOME AESTHETICS - Embodying a powder-coated finish, the ceiling diffuser vent exhibits resilience against flaking, scratching, and fading, granting your home or office space a contemporary appearance while maintaining a refreshing atmosphere. EASY INSTALLATION - Effortless installation is facilitated by the inclusion of three screws, making the process quick and hassle-free.