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I googled *microchip cat flap* and they directed me to the manufacturer's site (Pet Porte). I also contacted my local vet who confirmed that they could microchip the new kitten when he arrives.
Cat flap has been ordered and will be arriving this week so when it arrives, I will be passing it over to my builder to fix inside my new back door.
This sort of cat flap seems to be the only one of its type around and is definitely different to all the others.... I've had cats in the past and always felt sorry for them having to either deal with other cats knicking their food or having to wear those huge heavy magnetic collars....
I will still be asking Rifle to wear a little collar with his name and phone number on.... but that won't be as bad as the heavy magnets..