I like how Mass FX by Athletic Xtreme does one thing pure and simple….raise your testosterone level by up to 98% NATURALLY! As a natural physique competitor this is totally one of the best supplements on Earth. I love the simple process by which an athlete can boost his natural testosterone level by preventing SHBG (Sex Hormone Binding Globulin) from binding to testosterone. Your free testosterone instead binds to androgen receptors within muscle cells and sets the path for increases in muscle mass and strength. One of the best things about Mass FX that I like is it is FREE FROM NEGATIVE SIDE EFFECTS and is completely safe as it utilizes the body’s natural existing free testosterone to increase lean muscle mass. A+ supplement! 5 Star Rating!!!!!