Good idea but bad design
Just installed the dual flap... the opening is too small,,, our cats are quite big and they struggle to get through,, just. Our problem is one cat gets in and out ok, th other can't ,, its as if the sensors to get back in are too far back in the tunnel and should be nearer the front to allow the chip which is intheir collar to be read. After cutting more of my door away and fitting their window bracket, I still have same problem,,, cats can get out but not back in,,,useless for me now ..