Wheels and floor balls
Both wheels and floor balls give a hamster the exercise they need, in the wild a hamster can cover 5 miles in a night, so it is important that they get enough of a run in captivity. Wheels in the cage must be big enough for the hamster. As a rule I would say bigger is better, I have Roborovskis using medium 'silent spinners' and even comfort wheels with no issues, most my Syrians use 'comfort wheels' that are 9 inches. If your hamsters back is curving when it runs or if you notice it’s avoiding its wheel / running on top of it could be that the wheel is too small this hurts the hamster so best to go get a bigger one! Never use an uncovered wire wheel; this is because a hamster’s foot can slip between the rungs of the wheel causing potentially serious abrasions. If you have a wire wheel in, or any that has rungs use a strip of cardboard to over them by threading it around the perimeter.
Floor balls also need to be big enough for the hamster. Some dwarfs need a small floor ball; though I do have chunkier Campbell’s who need to use the same size as the Syrians. Dwarf balls are prone to breaking across the middle so I now tape the middle of a ball just to be sure, as an escaped Roborovski is a difficult thing to catch! With Syrian balls its best to get one that opens both ends, though I have usually found the hamsters quite happily jump in and out of them with no fuss. If they have never seen a floor ball they can be quite tentative about going in, but once they are in have a great time, by the second time they jump in happily! A hamster should only be left in its floor ball for about 20 minuets at a time, at which stage its best to put the back into the cage to see if they want some water or some food, or maybe go to the potty. If it then still wants to come out after a ten minutes break then I will usually let them. If you find the hamster is using its ball as a potty it maybe best to let it wake up longer before putting it in, though to some extent some will always wait till they are in the ball and all you will hear is rattling. You must never leave a hamster in a floor ball unattended. as mentioned earlier the dwarf balls can split in half, and many hamster figure out how to open them (usually by getting the ball trapped first) and of cause they can always be broke by the hamster running the hard into things (though my hamster are always clattering about they have yet to break one this way, though I still keep an eye out in case).