The e-Cat Electromagnetic Cat Door was designed with your Ideal Petfts safety and sense of adventure in mind. The Magnetic Collar allows only your pet to activate the cat door for easy and controlled access. Additional collars are available for multiple pet households and can be purchased separately. Features: For cats up to 25 lbs. Flap size 7in³ x 9in³ Cutout size 7.375in³ x 11.75in³ Door thickness range 1.25in³ to 1.75in³ Transparent flap features 4-way operation. Interior or exterior use.