I think theres more than one species and some get bigger than others. They might also call them ball anemones. I had a few pink tipped ones that were around 2". They are a mushroom coral but act like anemones that dont need light. Be careful if it gets bigger, mine ate alot of small fish included atleast 3 fairy wrasse, a sifting goby, a 6line, and maybe a mandarin. I tried killing them with a coat hanger since they were impossible to get to without dismantling alot of rockwork, they ended up splitting into more. I ended up chiseling them outta the rock and giving them to a lfs.
Usually they come as hitchhikers from atlantic rock from what Ive heard. Awhile back I seen a 6+" pink one that was very very nice looking. Good for a species only tank etc.