The endura flap thermo sash 3e installs, without the use of tools, into the track of your sash window. It features a beefy aluminum frame, LoE dual-pane glass and the energy efficient endura flap pet door. The endura flap pet door is manufactured to be flexible, safe and energy efficient in all climates. The transparent, dual-pane flap seals tightly against the outside weather using a patented system of magnets. When closed, the flaps significantly reduce air conditioning and heat loss. All doors come with locking cover and installation instructions. Endura Flap Pet Doors Flap Size: Large, Color: Bronze, Frame Size: 34" - 37"