The Endura Flap Custom Thermo Sash 3e Pet Door for Sash Windows delivers award-winning thermal insulation in a tool-free, non-permanent window insert. Built with a heavy-duty aluminum frame and dual-pane flap technology, it provides your pet with ultimate freedom while keeping your home secure and weather-tight.

Custom Sash Window Fit
Engineered to fit vertical sash window openings from 22" to more than 45" wide, this insert features built-in spring-loaded adjustment for a snug, draft-free seal. The non-permanent design requires window tracks at least 1" wide and installs without structural modifications, making it perfect for both homeowners and renters.

Extreme Weather Insulation
The patented polyolefin polymer Endura Flap remains flexible in temperatures down to -40°F. Magnetic closure strips line the flap edges to ensure a tight, wind-resistant seal that prevents drafts and maintains indoor energy efficiency.

Heavy-Duty Construction & Glass
Constructed with an extruded aluminum frame available in white or dark bronze, the insert utilizes single-pane safety glass to preserve natural light. Note that larger flap configurations with very narrow windows may require plexiglass inserts, or no glass at all.

Integrated Access Control
Each door includes weatherstripping and a sturdy top-loading Endura Flap Locking Cover, allowing you to quickly secure the flap and manage your pet's access when needed.