Not to down Hirocks, but just a little personal experience, FWIW. I've ordered from them - some smaller stuff for frags. The pieces I received were actually large (no big deal). However, this rock is very dense and heavy, and not very porous at all. I'd think you could use it for a few pieces, but I wouldn't use it for more than say, 10% - 20% of the rock in a reef tank.
HTH,