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MI-FLEX Adaptor 1mm - Ø 125 (20-125-MAE1)

National Flues proudly presents the MI-FLEX Adaptor 1mm - Ø 125, a quintessential component for transforming traditional rigid flue systems into modern MI-FLEX flexible flue liners. This essential adaptor, crafted in durable 316L stainless steel, is the ideal solution for those seeking reliability, safety, and performance in high-temperature applications. The MI-FLEX Adaptor is recognised as a leading choice in the UK for connecting single-wall flue systems with confidence, delivering a robust and efficient transition while maintaining compliance with stringent building regulations.
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£29.99
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At a Glance

  • Premium 316L stainless steel construction |
  • T600 temperature rating for high-heat applications |
  • Compliant with Building Regulations Document J |
  • Secure gas-tight seal when used with approved sealants |
  • Suitable for wood, oil, gas, and smokeless coal appliances

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At National Flues, we continuously monitor competitor prices. This ensures that we consistently offer you the best deals on all our products. Here’s how we keep your costs low:

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Price Match Guarantee: If you find the same product cheaper within 48 hours, we’ll match it and refund the difference.

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Have Questions?
Phone: 01670 206999
Email: [email protected]

The MI-FLEX Adaptor 1mm - Ø125 is a vital component in chimney installations, specifically designed to transition from a single-wall flue system to a MI-FLEX 316 or 904 flexible flue liner. Compliant with Building Regulations Document J, this adaptor ensures your flue liner is securely enclosed within a masonry chimney, capable of withstanding temperatures up to 600°C (T600 designation). Ideal for use with wood (less than 20% moisture), smokeless coal, gas, and oil appliances, this adaptor forms a gas-tight seal when installed with fire cement, ceramic rope, or high-temperature sealant.

SKU: 20-125-MAE1

Technical Specifications
SKU20-125-MAE1
Material316L Stainless Steel
Nominal Diameter125mm (5 inch)
Temperature Rating600u00b0C (T600)
Fuel CompatibilityWood (under 20% moisture), Oil, Gas, Smokeless Coal
ComplianceBuilding Regulations Document J, HETAS / CE
SystemMI-FLEX Accessories MF20
• Ensure the adaptor is installed within a masonry enclosure as per Building Regulations Document J. • Use high-temperature sealants such as fire cement, ceramic rope, or appropriate tape to secure a gas-tight seal. • Always confirm that the flue liner and adaptor diameters match accurately. • Follow manufacturer guidelines for proper clearance and positioning. • Keep the installation area clear of combustible materials and maintain annual or bi-annual chimney sweeps.

The main purpose is to connect a rigid single-wall flue system to a MI-FLEX flexible flue liner, ensuring a secure and compliant installation.

Yes, it is suitable for wood with less than 20% moisture, smokeless coal, gas, and oil appliances.

The adaptor can withstand temperatures up to 600°C (T600 designation).

You should use fire cement, ceramic rope, tape, or high-temperature sealant to make a gas-tight seal.

No, per Building Regulations Document J, it must be enclosed inside a masonry chimney.

Chimneys should be swept at least once a year, preferably twice if they serve solid fuel appliances—once at the end of the heating season and once before the new season.

No, chemical cleaners or mild steel tools should not be used. Always use appropriate stainless steel cleaning tools.
Delivery Information +

We work relentlessly to ensure you get your order fast. Estimated delivery for this product is Wednesday, April 30th. If you need faster stove or fireplace delivery please give us a call. We can often reduce longer lead times if we pay the carrier £25 for express delivery. Visit our Shipping Information page for more information.

Warranty & Returns +

All our products come with warranties. Mi-Flex offers a lifetime guarantee. Returns for damaged items are covered by insurance; non-damaged returns incur return delivery costs.

Price Match Guarantee +

We will match any price like for like on a retail basis. Give us a call if you find it cheaper and want to buy from us.

Read our review in our MI-FLEX Adaptor 1mm - Ø 125 buyers guide

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Experience the proven reliability of the MI-FLEX Adaptor 1mm - Ø 125 and upgrade your flue system today.

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