14-3/4"x10"x6' Single Wall HVAC Spiral Pipe. HVAC systems are a top-of-the line heating and cooling appliance that are used in residential and commercial applications. They demand duct that will deliver the air for maximized comfort. This 14-3/4"x10"x6' Single Wall HVAC Spiral Pipe is designed for underground and demanding commercial grade applications. The Spiral coils are designed for durability and added strength.