Nature's Blend Dietary Supplement Oyster Shell Calcium 500 mg with Vitamin D3 100 Tablets Double safety sealed for your protection. Do not use if either seal is broken or missing. Gluten Free. No Preservatives, Artificial Flavors, Wheat, Yeast, or Corn Added. This product is manufactured under strict quality control guidlines; therfore, purity and label potency are guaranteed. Oyster Shell Calcium may strengthen bones. Vitamin D helps your body absorb calcium and phosphorus.