End cap with EPDM rubber gasket | diameter 400 mm

End cap with EPDM rubber gasket | diameter 400 mm

Product description

End cap for regular round and Spiro ducts with a diameter of 400 mm. Made from pressed galvanised (using the Sendzimir process) steel for superior corrosion resistance. The end cap has a durable EPDM rubber gasket for a secure and airtight fit - this piece achieves airtightness class D according to EN 12237. Designed for easy and safe installation – a wider-diameter section of the spigot prevents over-insertion, while its rolled edge means there are no dangerous, sharp edges.
Diameter 1
400 Mm
Diameter 2
400 Mm

Additional specifications and description

What are end caps, and how are they used?

End caps are used by HVAC engineers to plug the open end of a round/Spiro duct. As such they are one of the basic building blocks of any ventilation system, small and large. End caps and reducers are crucial for longer duct runs to help maintain uniform air pressure and airflow speed. Thanks to the M1 hygiene certificate this end cap is suitable for most ventilation systems including in schools and hospitals.

Design and construction
The end cap is made from sheet steel that has been galvanised using the Sendzimir process ensuring that it is corrosion-resistant. It is press-formed into shape and the edge of the spigot is rolled to ensure that it is safe to handle. The spigot is designed to fit into a standard round or Spiro duct and features a rubber gasket for an airtight seal.
The EPDM material is very durable and long lasting and resists degradation from age and temperature. A circular fold with a wider diameter than the rest of the spigot will stop the cap at the correct depth and prevent its over-insertion. Alnor end caps combine durability, ease of use and airtightness with an attractive price, making them a great choice for your ventilation needs.


Thanks to the rubber gasket, even if the cap is slightly canted or there are minor imperfections in the duct, it should not pose a problem or cause air leaks. However, the end cap should be inserted and pressed into the open end of a round duct until it is fully seated and rests on the limiter.
The cap is permanently fixed to the duct using self-tap screws or rivets, without the need for any additional sealant. The elongated spigot is designed to provide enough space to safely drill holes for rivets with no risk of damaging the rubber gasket.

Mounting considerations

It is considered best practice to leave at least 50-60 cm of duct between the end cap and any take-offs, saddle pieces, diffusers, bends or reducers. This "empty" section of ducting at the end of the ventilation channel is, in fact, necessary for optimal ventilation system performance, especially at the end of long duct runs.
It is also important to never install take-offs on an end cap.

All Alnor ductwork elements manufactured from galvanised sheet steel with EPDM rubber seals conform to cleanliness class M1 and air tightness class D (according to EN 12237).

Please keep in mind that the final airtightness of the system is determined by several factors, including the installation method.

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