Customize Your Pet's Access - The SmartDoor™ features programmable selective entry, exit and auto-locking optionsPeace of Mind - The SmartDoor™ works with the waterproof SmartKey™ worn on your pet's collar; only the pets wearing the SmartKey™ can go in and outMultiple Pets - Great for households with multiple pets; programmable for up to 5 SmartKeys™Battery Operated - The SmartDoor™ is battery operated (4 D-Cell Batteries, not included)Door Installation - Designed for installation in interior/exterior doors; wall installation option available with purchase of Wall Install KitDoor Includes - Interior frame with flap, exterior frame, operating guide, cutting template, key ring, 8 mounting screws and SmartKey™ (both located in the battery door)Available in Two Sizes - Small for pets up to 15 lb, Large for pets up to 100 lb