2a,3a-epithio17a methyl-17b-hydroxy-5a-androstane (or Epistane) is a DHT derived prohormone. It binds to the androgen receptors that are found in skeletal muscle and muscle stem cells. This leads to a change in the muscle cell function and an overall increase in protein synthesis.

The compound doesn’t convert to estrogen (called aromatisation) nor does it hold water which can cause bloating.

Epistane in ROCk increases stem cell conversion to muscle cells whilst decreasing the conversion of stem cells to fat cells. You get the positive effects of muscle building and ensuring that your increase in weight is pure muscle and not water. Everyone is aiming for pure gains when it comes to building muscles and using prohormones and Rock will certainly help you to achieve that. 

It is classed as a highly anabolic compound, meaning it impacts predominantly on muscle tissue more so than exhibiting androgenic effects.