With the Kemp Pull Buoys you can Practice Proper Positioning during Swim Stroke, particularly for Freestyle and Backstroke. It helps Build-Upper Body Strength and Improves Stroke Technique by Isolating the Legs. It Enhances the Sense of Body Rotation in the Water. The Adjustable Pull Buoys are made of EVA Foam and are Virtually-Indestructible under normal use. The Kemp Pull Buoys provide an Excellent Low Impact Workout and are Blue and White in Color.