SureFlap Microchip DualScan Cat Flap, Brown Compatible with all common microchips - works with your cat's existing microchip to keep out intruder cats and wildlife Set exit permissions for each pet to keep specific pets indoors using dualscan technology - Store up to 32 pets Can be installed in doors, windows or walls - accessories available Door opening is 4 3/4" H x 5 5/8" W Requires 4 AA batteries which last up to a year with normal use (not included)