The Elite RFID cat flap has solved virtually all our cat access problems. Now only our cats can get in - no more food being eaten by other cats, no more spraying (yuk) by other cats when they get in (the BIG difference for us!) - which they did with the magnetic variety. They both learnt quickly how it works - it took about a week before they became experts. There are two slight down sides - one is that it is noiser than an ordinary cat flap (which certainly spooked the cats in the early days), and the other is that if the tag gets lost then the cat can't get in or out - I don't think that there's a setting that allows 'open access'. Just keep a spare tag and collar handy. The other great thing is knowing if the cats are in or out - we close them in the kitchen/utility area at night (stops midnight madness round the house so we sleep better), and knowing that there's one hiding somewhere means we can find it, put it downstairs and avoid the 2am cat jumping on sleeping head scenario! Highly recommended, even at the price.