Sulfate forms mobility and joint comfort NOW Extra Strength Glucosamine and Chondroitin combines two known joint support ingredients in their sulfate forms.Glucosamine is an essential block for the formation of glycosaminoglycans (GAGs) and proteoglycans, the main components of cartilage tissue.Chondroitin sulfate is a glycosaminoglycan that has been combined with Glucosamine in this product to support joint mobility and comfort.This extra strength product has twice the glucosamine and chondroitin (750 mg / 600 mg per tablet) as in our regular strength product (375 mg / 300 mg per capsule).There may be natural color variation in this product.