Medium oyster sea shell, 10 Pound. this is for medium grain, the second picture is the fine grain so you can see the difference This is the same oyster shell fine gravel I use it as substitution for Dyna rock, this is a little bigger grain as you can see on the picture of the fine, this size is better for mixing with soil, using oyster shell as top layer for seedlings avoid fungus keeping the top dry and clean, I use it also for mixing a special blend to plant a very valuable plants like lophophoras, aztekium, pelecyphora, ariocarpus, lithops, rare mesembs, or any plant that need a very good drained soil. For every item you add in quantity will be 1 item equal to 10 pound