I prefer the disks, if you continue to stack them under an acan or favia as the coral grows you get a perfect dome shape started.
They are heavy enough to keep larger frags and colonies from flipping over or being pushed around by the flow. I have no holes in my rock work for standard plugs with a shaft (I have all Tonga branch and shelf). I just use reef epoxy and stick these wherever I need to.
Good point above about them being ceramic instead of aragonite.
Looks real good
I have not used them yet but they should be great.
Nice heavy frag disks
I really like these frags disks. They are fairly large and are heavy enough to keep from flipping over or getting pushed around too easily. I like that they are ceramic instead of the aragonite and cement type that could potentially leach harmful substances into the tank. They also don't deteriorate over time like the aragonite with cement ones.