Skeleton Key contains a standardized extract from the bone of free-range New Zealand cattle and contains microcrystalline hydroxyapatite concentrate (MCHC), a complex crystalline compound containing calcium, phosphorus, bioactive growth factors, type I collagen, amino acids, glycosaminoglycans, and a broad range of essential trace elements. Skeleton Key also contains additional calcium and magnesium in the form of Albion^® minerals as well as Vitamin D in the form of cholecalciferol.