Selkirk - 3" to 8" Flexi-Sleeve (Flexi-Liner)

SelkirkSKU: AF4-FS

Sale price$65.37

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Size: 3 to 4-Inch
⛟ Estimated Delivery Date: Between and to all states excl. Alaska & Hawaii.

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Unleash the power of efficiency with Selkirk's Flexi-Sleeve – a revolutionary solution redefining chimney performance. Engineered with a robust poly exterior, this insulation sleeve is more than just a protective shield; it's your gateway to elevated draft efficiency and zero clearance wonders.

Designed for relining existing masonry or factory-built chimneys, the Flexi-Liner system is a game-changer for Category I natural gas or propane-fired appliances. Embrace the freedom of choice with diameters ranging from 3" to 8", offering flexibility for various applications. The 3000 series aluminum, 2-ply construction ensures durability, with a maximum flue gas temperature cap at 470°F.

Catering to diverse needs, our kits come in 25' and 35' lengths for 3" to 8" diameters, and 15' lengths for 3" to 5" diameters. Extend your possibilities with additional kits available in 10', 25', and 35' lengths. Adaptable to both neutral and negative draft gas appliances, our Flexi-Sleeve system boasts a Smart Choice warranty on all components, providing you peace of mind.

The ingenuity doesn't stop there – our B-Vent adaptor facilitates a seamless transition from all brands of Type-B gas vents. The insulation sleeve promotes rapid heat up, enhances draft efficiency, and allows for zero clearance between the liner and masonry chimney. Plus, with UL 1777 listing in the U.S.A., our product is a testament to safety and quality.

Seal the deal with Selkirk's Flexi-Sleeve – where innovation meets reliability for a chimney that stands out.


  • Elevates draft efficiency
  • Quick heat-up capabilities
  • Zero clearance between liner and chimney
  • Adaptable to neutral and negative draft gas appliances
  • Smart Choice warranty for peace of mind
  • Seamless transition with B-Vent adaptor
  • UL 1777 listed for safety and quality assurance


  • Tough poly exterior for durability
  • 3000 series aluminum, 2-ply construction
  • Maximum flue gas temperature cap at 470°F
  • Diameters ranging from 3" to 8"
  • Various kit lengths available
  • Extension kits for added flexibility
  • Smart Choice warranty on all components


  • Approval: Listed to UL 1777 in the U.S.A.
  • Cable Ties included for easy installation
Product Code
Part No Size
1740120 AF4-FS 3-Inch to 4-Inch
1750120 AF5-FS 5-Inch
1760120 AF6-FS 5.5-Inch to 6-Inch
1770120 AF7-FS 7-Inch
1780120 AF8-FS 8-Inch

Warranty: Lifetime Limited Warranty

Refer to the Smart Choice Warranty for full warranty details.


About The Manufacturer:


Selkirk products set themselves apart from the competition with their proven quality, safety, ease of installation, and lasting performance.  Selkirk is one of the most trusted brands in the industry because we stand behind everything we do.  From assisting with product selection, providing education and installation assistance, to our industry-leading warranties, we ensure your success every step of the way.

      Order Confirmation:

      Upon placing your order, you will promptly receive an email confirmation. Subsequently, we will conduct a thorough inventory check to ensure all items are in stock and available for immediate shipment. If your order aligns with the advertised delivery timeframe, we will promptly process it for shipment to our warehouse. In cases where the expected delivery time extends beyond the advertised timeframe, we will reach out to you via email and/or phone for confirmation.

      Order Shipment:

      Within one business day of your item being shipped, you will receive an email confirmation containing a tracking number. If you do not receive tracking information within six business days of placing your order, please don't hesitate to get in touch with us for assistance.

      Estimated Time of Arrival:

      Our typical delivery timeframe ranges from 2 to 10 business days. Custom-made products generally require 3 to 5 weeks for delivery. If the expected delivery date for your order would fall outside of the advertised 2-10 business day time frame, our customer service team will contact you to ensure your agreement with the revised timeline.

      Covered Areas:

      Please note that all estimated delivery dates and shipping costs advertised on our website apply exclusively to the Contiguous United States. For inquiries regarding shipping to Hawaii or Alaska, kindly reach out to our customer service team. While we do not offer direct shipping to Canada, we are more than willing to ship your order to the freight carrier of your choice.


      It is very important that you inspect the packaging of your items when they arrive and check if you received all boxes listed on the delivery receipt. If you notice any damage or shortage of packages, you must make note of it on the bill of lading, take pictures, and refuse delivery. Your note should say "refused due to damage". You must also take photos of all sides of the box and send them to us within 2 days. If there are no damages visible before opening the box, you must note "subject to further inspection may contain concealed damage". If you notice any damage after receiving the delivery, do not throw the box away, and contact us with the photos. After we receive information from you about the refused delivery or concealed damage, we immediately initiate a claim with the shipping company or with the manufacturer. After the claim is fully processed, we ship all replacements at absolutely no cost to you.

      Cancellations & Refunds:

      We offer free order cancellations before the shipping label or Bill of Lading is generated, or prior to the commencement of production for custom orders. Please note that custom-made items are not eligible for refunds once production has begun. To be eligible for a return, the item must be unused and in its original condition, with all packaging intact and in perfect condition. Orders delivered outside of the United States are not eligible for refunds. If your order arrives damaged, please refer to the "Damages" section. Our refund policy extends for 30 days. If 30 days have elapsed since your purchase, regrettably, we cannot process a refund. Prior to returning an item, please contact us to discuss shipping details. All refunds will be credited to the original credit card or PayPal account used for the purchase, within two days of receiving the returned items at our warehouse.

      Please contact for any questions regarding shipping time.

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      We believe that shopping should be easy, convenient, and most importantly, affordable. That's why we work hard to bring you the lowest prices on the products you love. But if you do happen to find a better deal elsewhere, we'll go the extra mile to make sure you get the best deal possible.

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