***We are out of 1/4" (6mm) plywood there is a global shortage. All grids will be 4mm thick. We will not take returns due to thickness since you have been notified*** This is a Tetrahedron Sphere Holder Crystal Grid made out of birch wood. These are made to order. You may choose between 8, 10 or 12 inches in diameter. Crystal grid and healing sets are groups of stones that go together for a purpose. You may choose just a center hole or all the holes as shown in the 2nd picture. Sphere holders allow you to set spheres on the crystal grids. Stones not included.