Dog Cat Flap Door with 4 Way Lock Security Flap Door For Cats Kitten ABS Plastic Small Dog Gate Cat Dogs Flap Pet Door Chip. Product Material: ABS material (smooth surface, very strong); 4 ways to set: not to enter (completely closed) / can be entered (completely open) / can only enter / only out. Size:L Outside size: height 25CM* width 23.5CM* thickness 5.5CM; Inner size: inner height 19CM* inner door width 18CM; Size:M Outside size: height 19.8CM* width 19CM* thickness 5.5CM; Inner size: height 15.5CM* inner door width 14.7CM; Size:S Outer size: height 19.8CM* width 19CM* thickness 1.8CM (suitable for installing glass doors and windows); Inner size: height 15.5CM* inner door width 14.7CM; Regarding the size standard of the opening when installing: the large opening height is 21.5cm and the width is 19.5cm; the medium and small opening height is 17.5cm and the width is 16.5cm; in addition, if the glass is installed, it can be opened again, as long as it is smaller than the cat. The outer dimensions of the door are OK, because there is no need to make screw holes on the mounting glass, and directly glue the glass glue or super glue