Have done a quite a bit of research on them. Finally broke down and bought a set. Makes a huge difference in the way you rotate your body on freestyle and backstroke...Love mine for my PERSONAL use. However, I am a size 34 waist...If you are buy 1 for someone with a waist size of a typical teenager, it WON'T fit. The strap that goes around your waist is desgined for bigger adult types. Really wanted it for my daughter who is 12 and it goes around her 2x...