Defender Body Fat Calipers are precision mechanical body fat calipers that have a Visual Pressure Indicator when correct results are obtained. Simply squeeze the caliper on the appropriate skinfold and the Indicator will turn from red to green, letting you know that you have achieved the correct pressure. You can let go of the caliper to read it as the unit also locks in the measurement for precision reading. Included is a Results Wheel Chart for easy lookup of body fat % after measurements are taken. This is a simple chart and all users have to do to calculate body fat is turn the wheel to line up their measurements with their age. Also included are instructions and charts to show where to take measurements for males and females. Plus, a body fat tracking chart is included as well.