FREEDOM - the ultimate convenience for owners, the offers your Pets the freedom and independence to come and go as they please. ADAPTABLE LOCKING - The 2 way locking system of the Original 2 Way Pet Door provides owners control over their pet’s movements, ensuring safety and peace of mind. EASY INSTALLATION - Fitting the Pet Door into thicker Doors has been made simple with the optional tunnel extension, included with the Medium and Large Pet Doors, (sold separately for the Small Pet Door)