Selkirk - 3" to 8" 10-Foot Extension Kit (Flexi-Liner)

SelkirkSKU: AFE10-03

Sale price$76.31
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Size: 3"x10'
⛟ Estimated Delivery Date: Between and to all states excl. Alaska & Hawaii.


Elevate your chimney's efficiency with Selkirk's Flexi-Liner 3" to 8" 10-Foot Extension Kit – the ultimate solution for relining existing masonry or factory-built chimneys. Designed for Category I natural gas or propane-fired appliances, this extension kit embodies reliability and innovation.

Crafted from the robust 3000 series aluminum with a 2-ply structure, our Flexi-Liner system guarantees durability and high performance. The 10-foot extension, complete with a coupler and fastener package, empowers you to tailor your chimney to perfection. Engineered to accommodate 3" to 8" diameters, this extension kit provides flexibility without compromising on quality.

Our extensions boast a maximum flue gas temperature of 470°F, ensuring a safe and efficient operation. Whether you choose the 25' or 35' lengths for larger projects, or the 15' option for more confined spaces, Selkirk's commitment to excellence shines through. Notably, the insulation sleeve not only promotes quick heat-up but also enhances draft efficiency, allowing for zero clearance between the liner and masonry chimney.

Listed to UL 1777 in the U.S.A, our Flexi-Liner extension kits offer peace of mind, complying with the highest industry standards. With a B-Vent adaptor available to transition seamlessly from various Type-B gas vents, Selkirk ensures compatibility across different brands.

Invest in your chimney's future with Selkirk – where innovation meets reliability.


  • Optimal Ventilation for Gas Appliances
  • Versatile Diameters: 3" to 8"
  • Robust 3000 Series Aluminum, 2-Ply Construction
  • Smart Choice Warranty Included
  • Insulation Sleeve for Quick Heat-Up and Enhanced Draft
  • Compatible with Type-B Gas Vents
  • Listed to UL 1777 Standards


  • 10-Foot Extension Kit with Coupler and Fastener Package
  • Suitable for Natural Gas or Propane-Fired Appliances
  • Maximum Flue Gas Temperature of 470°F
  • Available in 25', 35', and 15' Lengths
  • Zero Clearance between Liner and Masonry Chimney
  • Neutral and Negative Draft Gas Appliance Installation
  • Easy Transition with B-Vent Adaptor


  • Material: 3000 Series Aluminum, 2 Ply
  • Extension Kit Length: 10 Feet
  • UL 1777 Listed in the U.S.A
Product Code
Part No Size
1730010 AFE10-03 3"x10' Extension Kit
1740010 AFE10-04 4"x10' Extension Kit
1750010 AFE10-05 5"x10' Extension Kit
1755010 AFE10-05.5 5.5"x10' Extension Kit
1760010 AFE10-06 6"x10' Extension Kit
1770010 AFE10-07 7"x10' Extension Kit
1780010 AFE10-08 8"x10' Extension Kit

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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