Maintains insulation year round with dual pane, LoE glass in sturdy aluminum framing. Simple installation requires no tools, perfect for renters or vacation homes. Fits any sliding glass door with adjustable top or custom size. Weatherproof flap is 4-season friendly. Comes in 3 Colors Bronze, Satin, and White, 4 Flap sizes, Small, Medium, Large and Extra Large and three different adjustable track heights.