I believe its actually a 24" tire. Its a great commuter tire,and its good for trials. I wouldent suggest it for any off-road things. I have one and want to get rid of it because its not that great of a tire. you will probably find many things on the forum about this if you search for them.
There is a 20" fireball tire, but it isn't anything like the 24" cruser fireball that you'll hear people talk about. The 20" is just a basic BMX type tire with a cool fire tread pattern. I think it would be fine for freestyle riding, but not hopping.
I have one on my Bedford BC wheel. It has great style, but no special function.