Robos are the smallest type of hamster. They are seriously teeny. When the boys are in lounge mode and are fully stretched out, I think they're probably only about 3 inches long, so they're very pocket sized. (Literally!) They often live very happily together in groups, but ours fell out and now live separately, which they can also do well with. They are super fast and super active, and therefore probably not as easy to handle as other types of hamster, but they can become very tame and rarely ever bite.
We love them to bits and couldn't possibly be happier with our furry house guests, but I would be quite reluctant to recommend them to most people wanting a rodent friend. They can be not as easily interactive and tamable as other rodents, which isn't for everyone. I think you have to be happy to mostly just step back and watch their antics from behind the glass. Having said that, we have lots of fun out-of-cage time with Sputnik, but it's just really different from say, a guinea pig or a rat, who might cuddle with you for hours at a time. They just don't ever stop! For me, it's part of their charm.
This is Pintsize, who is the shy one of our boys! His favourite things are dried mealworms (no accounting for taste) and peeing in his wheel and looking at me expectantly until I clean it up so he can run it in again. (Never make the mistake of thinking tiny animals won't have you running to attend to their every whim, because they will.) He is a very lovely agouti robo with exceptionally fine whiskers - not that I'm biased, or anything.
There is also a possibly that there might maybe also possibly perhaps be another rodent on the horizon who might maybe perhaps potentially possibly be coming to live with us in the near-ish future, but more on that as it develops. Hopefully!