The Staywell Original 2-Way Pet Door by PetSafe allows your pets the freedom to come and go as they please. This pet door features a 2-way access system and includes a lockable interior barrier for convenient control over your pet's movement. It is designed for easy DIY installation with a provided cutting template and installation guide. While an optional tunnel extension for thicker doors and walls is included with medium and large sizes, it is sold separately for the small size. This durable pet door is suitable for brick walls, wooden doors, metal doors, and PVC/uPVC doors. It is weather-resistant with a self-closing, see-through magnetic flap. The door is ideal for cats up to 7kg (15lbs) and small dogs up to 3kg (7lbs). Overall dimensions are 236mm x 198mm (9 1/4 x 7 3/4), with a cut-out size of 180mm x 155mm (7 1/8 x 6 1/8). The maximum pet shoulder width is 147mm (5 3/4). The product comes with a 3-year manufacturer's warranty. PetSafe is committed to helping you and your pet live happily together.