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Thermo Sash 3e Pet Door for Sash Windows

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  • Durable and insulating pet door for windows
  • Dual-pane, Low-E glass and sturdy aluminum framing
  • Energy-efficient flap design keeps home insulated
  • Various flap sizes, colors, and adjustment ranges to fit your pet and your window
  • Strong and sturdy Locking Cover included to secure your home and pet
  • Tool-free installation, perfect for renters and vacation homes
Extreme Weather Resistance Extreme Weather Resistance
Install Multiple Install Multiple
Tool-Free Installation in Minutes Tool-Free Installation in Minutes

Size Chart

Flap Size Flap Dimension Height To Raise Window
Small 6" w x 11" h 18 1/2"
Medium 8" w x 15" h 22 1/2"
Large 10" w x 19" h 26 1/2"
Extra Large 12" w x 23" h 30 1/2"

For your adjustment range, you need to measure the length of your sash window track from the furthest left to right. The adjustment range of your pet door should ideally have your track length in the middle. Custom orders are subject to special restrictions. The following adjustment ranges are available:

  • 22"– 25"
  • 25"– 28"
  • 28"– 31"
  • 31"– 34"
  • 34"– 37"
  • 37"– 40"
  • 40"– 43"

Parts List

Thermo Sash 3e

1 window pet door

1 locking cover

1 center post weather seal draft stopper

1 foam weather strip

1 warranty card

1 installation instruction booklet

Popular Features

  • Highly insualting flap with a complete magnetic seal, designed to stay closed in winds up to 50mph
  • Complete magnetic sealdesigned to stay closed in winds up to 50mph
  • Polyolefin polymer flap keeps your home comfortable in temperatures between -40 and 110℉
  • Dual-pane, LoE glass gives you extra insulation for your home, pairs perfectly with newer energy-efficient windows
  • Four sizes available to fit cats to large breed dogs
  • Fits all vertical sliding sash window widths with a track width of at least 1"
  • Draft stopper and weatherstripping included for extra insulation and weather resistance
  • Easy, tool-free installation in a matter of minutes

There has been lots of discussion as to why the Endura Flap is such a high performing pet door, but for engineers or those looking for some more technical information here is a 74-page‚ dog door energy efficiency study‚ showing what makes it so special.

Need help Installing? Take a look at our Thermo Sash Installation page.

Replacement Parts and Accessories

Installing a Thermo Sash 3e

Variable Magnetic Resistance

Replacing the Flap in the Sash Pet Door

Switching Flap Sides

Wind Test

Endura Flap® Pet Door Warranty

Endura Flap products have a lifetime warranty against defects in materials and workmanship under standard regular use. Damage caused by not using the product as intended, improper installation and chewing is not covered under this warranty.

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