4" x 25 Ft. Flexible Semi-Rigid Aluminum Duct

4" x 25 Ft. Flexible Semi-Rigid Aluminum Duct by Lambro Industries

This 4 inch diameter by 25 foot long flexible semi-rigid aluminum duct delivers reliable, code-compliant venting for clothes dryers and other exhaust applications where traditional flexible ducts fall short. The semi-rigid aluminum construction means it will not collapse, sag, or kink during installation or operation, giving you a safer, longer-lasting vent run than vinyl or foil alternatives. Built flame resistant and durable, this duct is designed for professionals and homeowners who need a flexible solution that holds its shape and maintains airflow efficiency over the full 25 foot length. Lambro Industries engineers this duct to meet the demands of gas and electric dryer installations, bathroom exhaust systems, and similar venting needs where building codes require metal ducting.

Key Features & Benefits

• Semi-Rigid Aluminum Construction: The aluminum forms a flexible yet self-supporting structure that holds its shape without external framing. You get the routing flexibility of a flex duct combined with the rigidity and safety of metal, reducing installation time and eliminating the sagging and crushing issues common with vinyl products.
• Will Not Collapse, Sag, or Kink: The engineered corrugated design maintains an open airway even when bent or routed through tight spaces. Your dryer or exhaust fan operates at full efficiency because the duct holds its internal diameter, preventing airflow restriction and lint buildup that lead to fire hazards and appliance damage.
• Flame Resistant: Aluminum is inherently non-combustible and meets fire safety standards for dryer venting. This gives you code compliance and peace of mind, especially critical in dryer exhaust applications where lint accumulation and high temperatures create fire risk.
• Durable Material: Aluminum resists tearing, moisture, and temperature extremes far better than plastic or foil ducts. You install it once and it stays intact through years of use, eliminating the need for frequent replacement and reducing long-term maintenance costs.
• 4 Inch Diameter: The 4 inch size is the industry standard for residential dryer venting and many bathroom exhaust fans. This ensures compatibility with standard dryer outlets, wall caps, elbows, and clamps you already have or can source locally.
• 25 Foot Length: The continuous 25 foot run lets you connect appliances to exterior vents without splicing multiple short sections together. Fewer joints mean fewer potential leak points, better airflow, and faster installation on longer runs between laundry rooms and exterior walls.

Compatibility & Requirements

This duct is compatible with 4 inch dryer outlets on gas and electric clothes dryers, 4 inch bathroom exhaust fans, and other 4 inch diameter venting applications. You will need 4 inch hose clamps or foil tape to secure connections at each end. The duct ships in a compressed coil and requires two people to fully extend it to the 25 foot length, as one reviewer noted it takes effort to stretch it out completely.

Installation & Care

Route the duct with as few bends as possible to maintain maximum airflow. Secure each end with metal hose clamps and seal joints with metal foil HVAC tape, not plastic duct tape. The semi-rigid structure allows you to shape gentle bends and curves without needing rigid elbows, simplifying routing through walls, floors, and crawl spaces. Clean the interior periodically by disconnecting it from the appliance and using a vent brush or vacuum to remove lint and debris buildup.

What's Included

• One 4 inch diameter by 25 foot length flexible semi-rigid aluminum duct

Frequently Asked Questions

Q: Is this duct safe for gas dryer installations?
A: Yes. The duct is constructed from flame-resistant aluminum, making it suitable for both gas and electric dryer venting. The material is non-combustible and meets fire safety standards required for dryer exhaust systems, which is critical given the high temperatures and lint accumulation in dryer vents.

Q: How much of the 25 feet can I actually use when installed?
A: The duct ships compressed and requires stretching to reach the full 25 foot length. Multiple buyers confirm it measures 25 feet when fully extended, though one reviewer reported only achieving 15 feet without applying significant stretching force with two people. Plan to use two people during installation to pull the duct to its full length before securing the ends.

Q: Will this duct work with a 4 inch bathroom exhaust fan?
A: Yes. The 4 inch diameter is compatible with standard bathroom exhaust fan outlets. The semi-rigid aluminum construction is actually preferred over flexible plastic ducting for bathroom vents because it resists sagging, maintains airflow, and does not trap moisture that can lead to mold growth inside the duct.

Q: What is the difference between semi-rigid aluminum duct and regular flexible duct?
A: Semi-rigid aluminum duct holds its shape and will not collapse, sag, or kink like vinyl or foil flex ducts. Regular flexible ducts are softer and can crush under their own weight or if anything presses against them. The semi-rigid design gives you flexibility for routing while maintaining a consistent internal diameter for better airflow and code compliance.

Q: Do I need special clamps or fittings for this duct?
A: You need standard 4 inch metal hose clamps to secure the duct to dryer outlets, wall caps, and elbows. Reviewers confirm that metal hose clamps and HVAC foil tape are the correct fastening method. The corrugated aluminum accepts clamps easily and creates a secure, leak-free connection when tightened properly.

Q: Can this duct be used for HVAC applications?
A: This duct is designed for exhaust venting (dryers, bathroom fans) rather than HVAC supply or return air. While it is aluminum and durable, it is optimized for one-way exhaust airflow. For HVAC ductwork, you would typically use insulated flexible duct or rigid metal duct rated for conditioned air distribution.

Q: How do I clean lint out of this duct?
A: Disconnect the duct from the dryer and exterior vent, then use a long vent cleaning brush or vacuum with a flexible hose attachment to remove lint from the interior. The semi-rigid structure makes it easier to clean than fully flexible ducts because it does not collapse when you insert cleaning tools. Regular cleaning prevents lint buildup that restricts airflow and creates fire hazards.

Q: Is this duct UL listed or code compliant?
A: The product description states it is flame resistant and durable, and multiple reviewers mention it meets code requirements for dryer venting. One reviewer specifically noted that using semi-rigid aluminum duct can simplify inspections because you can potentially eliminate elbows in the duct run. Always verify local building codes, as some jurisdictions have specific requirements for duct material and installation methods.

Q: Will this duct fit through a standard 4 inch wall opening?
A: Yes. The 4 inch diameter is designed to pass through standard 4 inch wall sleeves and wall caps. The corrugated exterior adds minimal thickness, and the flexibility allows you to compress it slightly if needed to navigate tight openings during installation.

Q: Can I cut this duct to a shorter length if I do not need 25 feet?
A: Yes. You can cut aluminum duct to the length you need using tin snips or heavy-duty scissors. Cut cleanly through the corrugations, then secure the cut end with a hose clamp and tape to prevent sharp edges and ensure a proper seal at the connection point.