How to make order? 1 Quantity = 1kg of rocks. - We will pick the rock according the variants you select ( Mix, S, M, or L) - Please Note that if you need more Large Size of Rock please buy more quantity, 1x L size of rock may reach 1kg above. - You may add a remark on orders or inbox us for more details before purchase. Product Highlights : - Black Lava Rock is a porous aquascaping stone that is widely used for planted tank. - Provide growing space for beneficial bacteria. - Lava Rock do not harden the water.