*** We are out of 1/4 plywood there is a global shortage all grids will be 4mm thick. We will not take returns since we have notified everyone.*** This is a Crown Chakra Crystal Grid made out of birch wood. These are made to order. You may choose between 4, 6, 8, 10 or 12 inches in diameter. Crystal grid and healing sets are groups of stones that go together for a purpose. Sets of crystals and stones are used for ritual magickal or spiritual crystal healing purposes or with Reiki-Seichim energy work for healing.