The largest pieces will be about 6-7", but most will be about 4-5". Personally, I don't think this is very good to use as live rock. For one, it's ugly, but most importantly it isn't porous enough to promote anaerobic denitrification. I think the only use for it is to put in the sump if you don't want to spend a bunch of money on real live rock to fill your sump.
If you want to keep your costs down try using EcoRox from
www.bulkreefsupply.com read their shipping policies. Their shipping and brokerage is awesome.
