[SyrianNamedHarmony]

Originally Posted by AmityvilleHams

Hamsters and cats along with other predatory animals should absolutely not come into contact of any form under any circumstances - including in balls. There needs to be a secure door between them at all times.

Balls are their own issue though as they're quite unsuitable for a wide variety of reasons. It is impossible for a hamster to choose to get out on their own, there is extremely low ventilation which is bad for their respiratory health, they cannot willingly get water without human intervention(same with food, using the bathroom without it being inside with them, etc), hamster balls impair their vision(even clear ones), and they basically block all senses in general. Stick with a safe playpen(or similar alternative) for actual enrichment, though I wouldn't get a wire one as they're quite easy to escape from!

Yes balls do have many issues.