Actually I found the one I bought at GNC. They had a couple different brands and I just got the cheapest. It was around $20. The other models were digital and were around $50. As I understand it the calipers tell you what percent of your weight is fat. This also lets you determine what percent of your weight is considered lean mass (muscle, bone, organs, etc). Obviously you want body fat percentage to drop. However you DO NOT want your lean mass to drop which indicates that your body is losing muscle tissue. Its better if your lean mass remains constant OR even if it increases while you're dieting.