Come to Grainger for HVAC diffusers that disperse the airflow from ductwork. Use a round diffuser with overlapping stepdown rings with a butterfly damper. A square diffuser provides high volume air diffusion; multi-louver models control air volume. Perforated diffusers feature a clean, unbroken plane look and reduce noise in low volume air applications. Choose the type and size that fits your ductwork. Shop a wide selection of HVAC diffusers at Grainger today.