In reply to Simon Frost:
eco-balls are nothing like "pof". Pof is a resin, the whole point of which is to leave something behind to improve friction.
As someone else said, eco balls are simply metolius' own proprietary drying agent with a little bit of chalk mixed in as a carrier.
Metolius Super Chalk is lots of chalk with a little bit of drying agent added (i.e. the opposite of the eco-ball).
Eco balls leave next to nothing behind, and what is left behind can be blown away with a stiff puff! Far better than chalk - especially on well used grit boulder spots, which are becoming more and more unsightly with chalk build-up (and less fun working out the sequences when the chalk leads the way!)
I climb almost exclusively on grit, and actually gave up all forms of chalk due to skin problems for a couple of years. Started using Eco-balls recently (last few months) and they seem much kinder to my skin than MgCO3 chalk. However i am always careful to wash my hands and MOISTURISE.