Builders Best 11491 Semi-rigid Flex Aluminum Duct 4 in 8 Ft

Product Description

The BUILDERS BEST 11491 is a semi-rigid flexible aluminum duct section designed for residential and light commercial ventilation applications. Measuring 4 inches in diameter and 8 feet in length, it provides a durable, low-resistance airflow path between exhaust fans, range hoods, dryers, and exterior termination fittings. One end is crimped for easy slip-fit connection into downstream fittings, and the opposite end is plain for direct insertion into collars or elbows. HVAC technicians and installers rely on semi-rigid aluminum construction for its ability to hold shape while still allowing minor routing adjustments without additional fittings.

This duct section is suited for bath exhaust fan terminations, kitchen range hood exhaust runs, dryer exhaust transitions, and similar short-to-medium straight or gently curved runs. The semi-rigid aluminum construction resists crushing better than fully flexible foil duct, helping maintain consistent airflow and reducing static pressure drop across the run. It is commonly used in new construction and renovation work where a clean, code-acceptable exhaust path is required.

Key Features

• 4-inch diameter fits standard bath exhaust, range hood, and dryer exhaust collars
• 8-foot length provides adequate reach for most short exhaust runs without splicing
• One crimped end and one plain end for straightforward slip-fit installation
• Semi-rigid aluminum construction holds shape and resists crushing better than flexible foil duct
• Smooth interior surface reduces airflow restriction and lint accumulation in dryer applications

Compatibility

Designed as an OEM-style replacement and new-installation duct section for 4-inch exhaust ventilation systems including bath fans, range hoods, and residential dryer exhaust applications.

Installation Notes

Installation is typically performed by HVAC technicians, sheet metal workers, or licensed contractors following local mechanical codes and IRC or IMC exhaust duct requirements. Secure all connections with approved metallic foil tape or approved clamps — do not use standard duct tape on exhaust runs. Minimize bends and keep the total equivalent length within the appliance manufacturer's maximum duct length specification. Power down any connected appliance before making duct connections.

Technical Specifications

• Diameter: 4 inches
• Length: 8 feet
• Material: Aluminum
• Construction: Semi-rigid flexible
• End Configuration: 1 crimped end, 1 plain end

Standard Information

• Brand: BUILDERS BEST
• Manufacturer Part Number: 11491