Yeah, caps. They can grow pretty fast in good condition. You can get them to be that big in about 3 years to 4 yrs. from quarter-sized frag.
The one right between the yellow circles looks like a nice cap that got encrusted onto the back (overflow). If that is a cap, you can see the nice column form in the middle of the colony.
They are probably one of the most traded corals out there. Very easy to find. Again though I would start with the softies first and work with them and then move up to SPS.
