Free U.S. Shipping & Lifetime Warranty For All Endura Flap Pet Doors

Dog Doors for Windows

  • Effortless and non-permanent installation with the spring-loaded design, adaptable to most vertical or side-sliding window heights. 
  • Weatherproof flap withstands -40 degree temperatures and stays shut in 50mph winds
  • Low-E glass provides UV and infrared resistance for maximum insulation value
3 products

Window TypeUp and Down Sliding WindowLeft and Right Sliding Window
Insulation LevelHighHigh
Pet Size< 30"< 21"
Frame MaterialMachined Aluminium FrameMachined Aluminium Frame
Climate TypeSevere 4-seasonSevere 4-season
Wind Resistance40 mph40 mph

Measuring Your Pet for a Window Pet Door

It’s vital that the flap of your window pet door is the perfect size for your pet. A door that is too big will be difficult to open, but one that is too small can be uncomfortable to use and may even cause pain after long-term use. 

Before you order your pet door, make sure you measure your pet to ensure that you have selected the best size for them. It’s best to measure your pet from their paws to the highest point of their back, adding an additional one or two inches on top to ensure that their back does not scrape the top of the door.

If you have pets sharing the same door, it’s best to measure the height of the tallest pet. However, a smaller pet may have trouble opening a door that is too tall for them. That’s why you can adjust the magnet strength on every Endura Flap Pet Door. If the door is too heavy to be opened, you can remove some of the magnets to make it easier on your smaller and more timid pets. 


How to Measure Your Window Track

You’ll need to measure your window track to choose the correct pet door panel height. Make sure to measure the track thickness, which needs to be at least 1” to accommodate the panel.

Sash Windows: For sash windows, measure from the deepest point of one side of the track all the way to the deepest point of the other side of the track to find the track width. 


Side-Sliding Windows: To measure your track height, use a tape measure to find the distance from your bottom track to your upper track. 


Locking & Security 

Locking the Flap: Every Endura Flap Pet Door comes with a molded ABS plastic Locking Cover that slides over the flap opening to prevent unwanted critters from getting in and out of your home while you’re away. 

locking cover locking cover

Locking Side-Sliding Window Panels: All Endura sideways-sliding window inserts come with a C-Clamp Lock. The clamp lock attaches to the flange of the window track at the edge of the sliding window panel. This clamp securely locks the window to prevent access while you’re away. When you want to open your window, simply remove the clamp lock. For additional security, we recommend a wooden dowel or Charley Bar. The Charley Bar can be unlocked in a matter of seconds to open your sliding window. 

Locking Sash Window Panels: To permanently lock your Endura Sash Window Insert, you can install wood screws in the track immediately above the window on both sides. With this method, you would no longer be able to raise the window. For continued use of your window sash, the Charley Bar is the perfect solution. It unlocks in just a few seconds so you can access the sash window.


Features of the Endura Flap Pet Door

Endura Flap Pet Doors are top of the line in quality, durability, and insulation value. All Endura Flap doors are made in the USA, designed and manufactured in San Luis Obispo, California. Check out the unique features that make the Endura Flap the best pet door

Environmentally Friendly: The non-toxic Polyolefin Polymer Flap is safe for your pets and the environment. Most pet door flaps are made of vinyl (PVC), one of the most environmentally damaging plastics to produce. The production, usage, and disposal of PVC releases toxic, chlorine-based chemicals into the environment.  The polyolefin polymer used for the Endura Flap is recyclable and safe. It is commonly used in food packaging, and its production does not produce any toxic fumes.

recycle your flap 

Award-Winning Flap: In addition to being environmentally friendly, the Endura Flap is made to withstand extreme heat and cold to keep your home insulated. Whereas most vinyl pet door flaps are about ⅛” thick, the Endura Flap is ⅞” thick. The sealed flap unit is slightly thicker than dual-pane glass and provides a similar level of weather protection.  The flap unit is translucent for maximum ease of use by pets of all sizes. The flap’s interior is divided by horizontal barriers to reduce the effects of air currents moving within this space as it continuously heats and cools.

inner flap design

Severe Weather Protection: Every component of the Endura Flap Pet Door was designed for extreme weather protection. The flap is treated with UV-resistant retardant, preventing shrinking, warping, or yellowing in the sun. It is attached to an architectural extruded aluminum frame for additional durability. All Endura Flap models, single and double flap, protect against temperatures from -40℉ to 110℉, as detailed in this energy performance study. In addition, magnets line all three edges of the pet door flap for 50 mph wind resistance.

UV retardant design great for cold weather 

Superior Manufacturing: The weather-resistant flap rotates on a rod instead of attaching to screws, preventing the warping and tearing common in standard pet doorsThe magnets lining the flap are customizable, meaning you can adjust the magnet strength for timid pets or for increased wind resistance. 

magnetic flap design

High-Aspect Ratio Flap: The safe, flexible Endura Flap has a high-aspect ratio. Most pet door flaps are not very high for their width, meaning you need to install the door higher up to accommodate your pet’s height. With a high-aspect-ratio flap like the Endura, you can install lower to the ground so that your pets can manage the step-over even as they grow older.  

flap measurements


Frequently Asked Questions

Why aren’t these available in larger sizes?

Most windows are not big enough to accommodate the larger pet door sizes. Plus, due to their position in the home, window pet doors are best used for cats who are entering the backyard and an enclosed catio. A cat door for window is a great way to provide your cat the freedom to come and go. 

How are the Endura Flap Pet Doors for Windows secured to my window?

The window inserts have a spring-loaded design, which means that they use pressure to stay secured to your window track. If you are looking to install the pet door panel semi-permanently, then you can screw it into the track. You can loosen the screw whenever you are ready to remove the window panel. 

How do I lock the window pet door?

If you want to keep your pet from going in or out, you can use the locking cover to block access to the dog or cat door for window.

But if you want to prevent people from opening your window, you will need to insert a dowel or a Charley bar to hold your sliding window pane in place against the window panel. This works for both horizontal opening and sash windows. 

Will the Endura Flap window dog door keep out the weather?

Yes! Even if there are no double flap options, all Endura Flap products are made with insulation and energy efficiency in mind. Every flap is lined with magnets to create an airtight seal, and you can add weather stripping around the panel to block out any drafts. 

Every Endura Flap window pet door insert is also made with Low-e glass, which prevents sunlight from heating up your home during the summer. Just as our magnetic door flap prevents your heating bills from going up, the Low-e glass prevents your cooling bills from skyrocketing as well. 

Is it possible to switch which side of the Thermo Sash 3e that the pet door is on?

Yes, it is! Just follow these few easy steps: 

  1. Remove the screws on the top and bottom of the flap assembly.
  2. Slide the flap assembly out of the window panel.
  3. Flip the flap assembly upside down and slide it back in.
  4. Secure the screws and install the pet door back into your window track. 
  5. Test to make sure the pet door is secure and working properly. 

How do I make the Thermo Sash 3e smaller than the 22” adjustment height minimum?
You can trim down the spring-loaded piece on the side of the Thermo Sash panel, which will give you an extra ¾” of compression. This will allow the panel to fit doors that are about 21-¼”.  Due to the glass in the window panel, you won’t be able to make it any smaller. 

Your Endura Flap Pet Door is not wide enough for my window, but only by an inch. Do I have to order a custom size?

Nope! You can add a width extension to make your panel fit your window. Start by cutting a board to the height and length you need. Then slide it into the adjustment channel on either side of the door. 

Is installing a window pet door easy? 

Installing a window pet door panel is very easy. The spring-loaded adjustment piece at the top allows for tool-free installation and removal in just a few minutes. See the Sash Window installation page and Sliding Door installation page (a side-sliding window is essentially a mini sliding glass door, so the install process is the same) for more details.  See our installation video archives to learn about other installation options.