Dog Door Info Please

[JaxD]

Hi all

We'll be getting our Jack Russell puppy in 2 weeks and 2 days time.. (not that I'm counting the days or anything! :-) ) We are going to buy a Staywell dog door for when he's older but the small size says for CATS up to 7kg and DOGS up to 3kg (and shoulder width of 14.5cm). But the medium says for dogs up to 18kg like beagles and spaniels. Since an adult Jack Russell is usually around 6kg, I'm confused as to which size to buy as the medium just seems huge.

Do any DOL'ers out there have Jack Russells (or similar size dogs) that use the small Staywell door?

Any advice would be much appreciated!