AC Infinity Air Filter Box with High Efficacy Filter, 4-InchDescription Duct Filter Box: This product is engineered for use with inline fans, enabling fresh air circulation and blockage of dust and odors. It is constructed with 1mm thick cold rolled steel alongside aluminum duct flanges, ensuring durability and the ability to withstand extreme weather conditions. Efficient Design Features: A slide lock door offers easy accessibility to the inner chamber, while its soft neoprene layer serves to create a dust