Compatible with: [SureFlap Microchip Small Dog & Cat Door] (https://www.chewy.com/sureflap-microchip-small-dog-cat/dp/157131).
To install in glass or walls, use SureFlap Cat Door Mounting Adapter.
Be careful, there are multiple sizes of "small cat & dog door" so you need the correct extenders. Chewy needs to clarify the part number. For example, in my SureFlap Door instruction manual it says mine matches with extender number TUN101.
Would have been great if I had measured first... I ordered one extension, turns out I needed two for a wall install. Otherwise the tunnel extension came fast and attaches to the petdoor like it should. Now I'm waiting for a second one to ship out so I can finish my install.
If you need these to extend the tunnel through a wall, like I did, make sure to tape them on the outside like the instructions say. The plastic is fairly thin and gaps will appear at the joints as it flexes. I also made sure the bottom was supported by putting wood shims under it. I didn't want the floor to sag when the cat moved through it. Suggestion for filling the gap between these extensions and the outside trim piece: Use foam tape applied either on the outside of the extender (it it is accessible) or in the inside of the trim piece . Don't get me wrong, I like the product. The pieces fit together nicely and it was the perfect way to get the door installed in our wall.
This extender does not fit the small cat flap, it’s far too large the product description is wrong
It is a great product, works perfectly for my dogs that are so happy now!
even though this is a UK designed item, manufacturer is making a bundle of $$ in the USA, so why not accommodate North American building standard residential construction instead of tunnels for brick and mortar thick walls from the UK and make various tunnel extenders at incremental sizes other than only 2" increments, like say 1.0",1.5", 2.5" 3.0" - or are the extenders suppose to stick out that much (over an 1.5") and if so the edges of the plastic extenders seem kind of too sharp edges that may hurt cats and dogs as they are going in and out of the tunnel...poor design!
I no longer get woken up by my dog 2-3 times per night to go outside! This is a life saver paired with the petsafe door. Hallelujah!
I love the SureFlap Door. It has helped train our puppies to use the potty outside. The only reason I rated it a 4 was because there is some space between the frame and the door itself. I worry about the winter time and heat escaping and cold weather entering.