High-quality insulated flexible ducting for HVAC, hydroponics or air ventilation. 4-inch diameter, extends up to approximately 25 feet (estimate). Constructed with a flexible inner core, thick fiberglass insulation to reduce heat loss and noise, and a durable outer vapor barrier. Still in original plastic wrapping and unused. Perfect for connecting inline fans or vents in grow tents, bathrooms or HVAC systems. Similar 4” x 25’ insulated ducts retail around $25–30 new; I'm asking $20 for a quick sale.