Anti-Estrogen or Estrogen Blockers are supplements used to deter the conversion of Testosterone into Estrogen. Testosterone is necessary to build muscle, gain strength and achieve a lean physique. When testosterone levels rise, estrogen levels rise in accordance. Estrogen inhibits your ability to build muscle and burn fat effectively, and when Testosterone levels are high, there is a chance that some of that Testosterone will convert into Estrogen. Therefore, Estrogen Blockers work by inhibiting the Aromatise Enzyme which enables this process, allowing you to maintain high Testosterone levels, a MUST for physique-enhancing goals.