Not so suitable for large cats
We bought this as the ideal solution to stop a local stray Tom from coming in and spraying the house. Managed to get one cat's chip recognised without problem, but the other cat who is of a larger size (7+kg) struggled with it on two counts. Firstly he found it difficult to belly crawl through the smaller inner square aperture of the flap (although the outer tunnel is larger, the inner flap narrows at the bottom to a square), and also his microchip is placed far enough down his upper back that the flap did not register the chip even when his nose was firmly squashed against the flap trying to open it. It was amusing to watch his efforts, but in fairness it was not suitable for big Boy!
Zooplus, to their credit, agreed to return and refund without issue.