40mm or approximately 1-/8 inches across. Facets spanning out from the smooth circular center giving it an optical allusion of a hole. Faceted both front and back with a slight rounding. This sun prism has the most facets of any I have seen coming from the center. This unique cut is produced by an Austrian maker other than the famous maker. The more facets the more rainbows a prism produces and this one creates loads of rainbows. Perfect size for a pendant. There is a hole at the top to hang it by. Your prism will come gift boxed with a bow as pictured.