Button polyps/palys - they are good
simmilar to these https://www.saltwaterfish.com/site_11...ot_parent_id=4
If you have any super slow growng corals I wouldn't put them near them as they grow quite fast but not a bad hitchhiker
Mid to low depth. medium flow. Like Keri said, they can be aggressive growers. Fortunately in my tank, they been a little slow. But I like the heck out of them.