Sport Performance. Ultimate Bodybuilding Product. Promote lean muscle gains. Increase protein synthesis. Reduce estrogen levels. Built with Lethrosterone. Boost testosterone. Mass 550 by FinaFlex is the most pivotal advancement in lean muscle acquisition ever introduced. Mass 550 contains two of the most innovative and exotic bodybuilding ingredients available today. The novel combination of Letrosterone and Maslinic acid creates an anabolic environment that promotes lean muscle growth, increased protein synthesis, and a reduction in overall estrogen in the body.