Polyester Blinds width will 2/5" narrower for a snug internal installation. Actual Blinds Size is 29 3/5" x 64" H. Choose the size SAME or CLOSEST to your window width for INSIDE mount. For Example, if your windows are 30" wide, order 30" or slightly less for internal installation. For OUTSIDE mount, we recommend order (2-4)inch wider than your window width for better coverage. For Example, if your windows width is 30", order size 34" would be okay for outside mount. LazBlinds patented technology mechanical top-down/bottom-up stopper prevents the bottom rail from lifting the middle rail. By adjusting the position of the middle rail you can adjust the light and air circulation at will. REAL Blackout Shades: The silver-plated layer inside the cell can completely keep out the sunlight and uv ray. Offering a real dark environment, bringing you a good night's sleep during the day. Perfect for bedroom. Cordless Blinds for Windows: The cord-free design provides a clean, tangle-free look to the window and creates a safer environment for children and pets. Easy to raise up or lower down to gently filter sunlight. (Pls Note) For INSIDE mount, window frame should have at least 1 1/5” depth. We provide customized size services. If you have any issues or questions in the process of purchasing, installing or using, please feel free to email to us by Amazon message and we will respond to you within 24 hours.