hamster cages

the minimum size a hamster cage needs to be is 450sq inches (US) and 720sq inches (UK), this is only the minimum cage requirements so I would aim to go larger just to provide all the necessary items and enrichment .if you are going to add cage extensions or levels to the cage, this does not go towards the floorspace and instead provides extra enrichment and hamster must be provided with an open area of 450sq inches (US) and 720sq inches (UK). 

Hamster wheels

when it comes to wheels for hamsters ,Syrians require an 8-12 inch and dwarf hamsters require a 6 inch and above, but I would always aim to go larger. If you give your hamster a flying saucer they still require an upstanding wheel as flying saucers doesn't replicate an upstanding wheel