Rep-Cal Calcium with / Vit.D-3 3.5 oz. size. Rep-Cal Ultra-fine Phosphorus-free calcium supplement with Vitamin D-3 is used to balance Calcium/Phosphorus ratios for preventing Hind-Leg Paralysis disorder. Contains only 100% natural oyster shell Calcium Carbonate for its Calcium source plus added Vitamin D3 to aid with absorption. Veterinarian recommended. Manufactured by Rep-Cal.