OYSTER SHELL CALCIUM D, TAB 2550MG (100/BT 12BT/CS Oyster Shell Calcium Tablets Plus Vitamin D Plus Vitamin D. 250 mg Calcium-enhanced absorption. Nutritional supplement. Compares to Os-Cal® 250. Not Made with Natural Rubber Latex. Packaged: 100 Per Bottle, 12 Bottles Per Case Os-Cal is a registered trademark of GlaxoSmithKline.