Woot offers iPower Flexible 4 Inch 8 Feet Aluminum Ducting 4 Layer Protection Dryer Vent Hose for HVAC Heating Cooling Ventilation and Exhaust, 2 Clamps Included, Black for $6.97 (orig. $9.20). Free shipping for Prime Members.

Product Description:  
Ducting size: 4 inch; length: 8 feet; material: PVC thermoplastic; inner material: aluminum foil. Temperature range: -22°F~212°F(-30℃～100℃) Features: 1.Perfect for ventilation applications including HVAC, kitchens, dryer, bathrooms, greenhouses, grow rooms, grow tents, etc. 2.High-quality aluminum foil, high temperature resistant and corrosion resistant, long lasting. PVC thick layer on this ducting can prevent light leaks. 3.Four-layer design (PVC layer + Aluminum Foil + PET + Aluminum Foil) makes it more durable and resistant to leaks, tears, and cuts. 4.The aluminum foil duct tube can bend in any direction, allows you to accommodate most space restrictions. Flexible length for inline fan, quick and easy to set up. 5.Include a pair of 4 inch stainless steel duct clamps, rustproof and corrosion resistant. Variety of applications: Suitable for any ventilation & air conditioning (HVAC) purposes, move and deliver air in kitchens (cooking exhaust), green houses and grow rooms (air circulation, intake, exhaust and light fixture cooling), bathrooms (smell and moisture exhaust), grow tents and other applications.

• Variety of applications: perfect for HVAC ventilation, grow tents air circulation, green houses and grow rooms air intake and exhaust or light fixture cooling, kitchen cooking air exhaust, bathroom smell and moisture exhaust, etc
• Specifications: ducting size: 4 inch; length: 8 feet; material: PVC thermoplastic; inner material: aluminum foil. Temperature range: -22°F~212°F(-30℃～100℃)
• Premium material: high-quality aluminum foil, high temperature resistant and corrosion resistant, long lasting. PVC thick layer on this ducting can prevent light leaks. Include a pair of 4 inch stainless steel duct clamps
• Four-layer design: four-layer design (PVC layer plus aluminum foil plus PET plus aluminum foil) makes it more durable and resistant to leaks, tears, and cuts
• Flexible ducting: the aluminum foil duct tube can bend in any direction, allows you to accommodate most space restrictions. Flexible length for inline fan, quick and easy to set up