After one day and night, it works like a dream. Pussy not too happy with us having to hold his head in the flap for it to recognise his chip; and we only got mauled the once. Flap is so see-thru that we keep thinking it has blown off. Unfortunately, the old one we removed of the same make did not allow us to fit the new one using the previous screw holes and we had to make two new ones. We can now be sure that next doors cat is not making nocturnal visits; our cat is so well fed he just sits there watching him eating his grub. Ours is big, ginger and bushy and looks dangerous, but is daft as a kitten. Wish we'd got this new microchip flap years ago.