[cypher]

Anything up to but not above 1cm is fine, unless it's a tiny baby robo or chinese 1cm is no problem for dwarf hams.
Personally I prefer barred cages for my dwarfs but as I said you would need to be very careful setting up an alaska, a safer (although more expensive) option is something like the Hamster Heaven (I don't advise using the tubes or penthouse though) or the Savic Mickey, both have good bar spacing & plenty of room for a dwarf but aren't so high so you don't have the same concern about falls.

The Kerry is a nice tank but hard to manage as it weighs a ton!