Bone Builder® Extra Strength provides bone health support with microcrystalline hydroxyapatite concentrate (MCHC), a highly absorbable crystalline compound comprised of naturally-occurring components of bone which is backed by over 30 years of research. MCHC contains naturally occurring calcium, phosphorus and trace amounts of other minerals, bone growth factors, collagen, and other vital bone proteins. Each serving of just three tablets provides over 1,000 mg of calcium. Gluten free and Non GMO.