The APK Warm Air Duct for Diesel Heater and Parking Heater features a three-layer design of cardboard, aluminum, and plastic, offering superior heat distribution and durability. The cardboard provides flexibility and lightweight support, while the aluminum reflects heat to prevent energy loss, and the plastic exterior protects against moisture and abrasion. This duct is ideal for HVAC systems, industrial heating, and automotive applications, offering excellent thermal efficiency and ease of installation. Its robust construction ensures long-term reliability, making it a top choice for any environment requiring consistent warm air distribution.