Anyone know what media this is?

Title says it all. It kind of looks like rock wool cubes but I'm not sure. Anyone?

That is growstone.
http://www.growstone.com/about/products/hydroponic-substrate/

Looks like rockwool chunks to me, too. Wish I could get more of a close of your pics...

Chunky Stool said:

That is growstone.
http://www.growstone.com/about/products/hydroponic-substrate/

Click to expand...

It looks more like rockwool.

Hmm... looks like the consensus is rockwool.