All grids will be 4mm thick. We will not take returns due to thickness since you have been notified*** This is a Owl Dreamcatcher Crystal Grid made out of birch wood. This grid is 4 inches in diameter. . All grids are 4mm thick. 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.