Exercise balls divide opinion among small-animal keepers, and it is worth understanding why before you buy one. A hamster inside a ball cannot see or smell where it is heading, cannot stop where it wants to, and cannot get out. Used for a few minutes with you watching, it is a change of scene and a bit of stimulation. Used as a hamster's main source of exercise, it is not enough.

The ball is a clear sphere with ventilation slots around it and a lid that locks shut, and the current listing describes it as 20cm across. Three colour options exist and stock is supplied at random, so it arrives in whichever is on the shelf. The clear shell is the whole point: it lets you keep your eye on your hamster throughout, which is the only way one of these should ever be used.

• Clear plastic sphere with ventilation slots
• Locking lid
• Listed at 20cm diameter
• Three colour options, supplied at random
• Suits hamsters and similar small rodents

Two things worth knowing. A 20cm ball suits dwarf hamsters. A Syrian needs more diameter than this to run without arching its back, for the same reason a Syrian needs a 28cm wheel where a dwarf manages on 20cm. And a ball is no substitute for a proper solid-surface wheel in the cage plus supervised floor time in a blocked-off area. Keep sessions short, stay in the room, and keep it well away from stairs.

Who it's for: Dwarf hamster keepers wanting a brief, closely supervised change of scene, not those looking for their pet's main daily exercise.