Adjustable to fit 4", 5", and 6" duct. For bathroom and kitchen fan venting. Outer grill and flap prevent unwanted pests from entering home. Stylish flush mount design is paintable to match the exterior color of home. Leakproof collar to duct connection prevents moist air backdraft. Includes: Installation instructions, stencil template, and 3 mounting screws. Tools required: Drill with driven attatchment, saw, utility knife (if connecting 5" duct), and metal clamp (same diameter as duct).