Norse Mythology design. Norse mythology Celtic Tree of Life, Yggdrasil. This zen design is a perfect gift for men and women with Scandinavian roots, Viking heritage, or interested in Celtic religion Adhesive backing attaches the PopGrip to your case or device. Will not stick to silicone, leather, waterproof, or highly textured cases. Works best with smooth, hard, plastic cases. Not compatible with wireless charging Printed top is swappable with other compatible PopGrip models. Just press flat, turn 90 degrees until you hear a click and remove to swap.