There are three types of glucosamine: Glucosamine Hydrochloride HCl), N-Acetyl Glucosamine, and Glucosamine Sulfate. Both glucosamine HCl and glucosamine sulfate are rapidly converted into "free" glucosamine in the stomach. So, as per a medical basis, they are equally as effective. However, glucosamine HCl is 79% glucosamine while glucosamine sulfate is only 47% - 52% glucosamine. This means that products containing 500mg glucosamine HCl have more glucosamine than products containing 500mg of glucosamine sulfate. Our Move Free® and Schiff® Glucosamine products primarily contain glucosamine HCl, providing consumers with a higher percentage of glucosamine than many of our competitors who use more glucosamine sulfate in their products.