Size options S: Outer size: 19*19.7*2cm; Inner size: 16*15.7cm M: Outer size: 19*19.7*5.3cm; Inner size: 16*15.7cm L: Outer size: 25*23.5*5.3cm; Inner size: 19*18cm XL: Outer size: 25* 5.5*27.7cm; Inner size: 22*20cm Key features and benefits Clear visibility and weather protection Transparent flap lets pets see through the door while the exterior screen provides waterproof protection. The design minimizes drafts and keeps the interior environment more stable. Energyefficient and quiet operation Brush strip reduces energy loss and promotes silent action, so pets and occupants won't be disturbed during use. Flexible access control with four modes Fourway lock with red and green labeled switches enables easy adjustments. Settings include open, only outside, or completely locked, making it simple to manage pet movement as needed. Petfriendly flip cover Transparent flip cover is preferred by many pets, offering a smooth, sealed closure that helps maintain climate control. The flip cover works with a sealing mechanism to reduce energy loss and keep noise to a minimum. Compatibility and performance notes Four size options (S, M, L, XL) provide a range of fit for different cat sizes and doorway configurations. Outer and inner dimensions are specified for precise selection to suit your door opening and pet size. The combination of a transparent flap, waterproof exterior screen, and brush strip aims to provide reliable performance while minimizing disturbance for both pets and household occupants. Use scenarios Scenario 1: Home with both indoor and outdoor access for a cat. Install in an exterior door to allow your cat to come and go while keeping weather elements out. Scenario 2: Household needing schedule control. Use the lock modes to restrict entry during nighttime or when you want to prevent entry while still allowing exits. Scenario 3: Multiroom or splitlevel home. The range of sizes lets you place the cat door in different doorways without compromising fit or function, while maintaining quiet, energyefficient operation.