4D-BOL uses the closest legal chemical cousin to testosterone, 4-DHEA to give your body all the raw materials to make more testosterone. 4-DHEA is a throwback prohormone to the original “ANDRO” and we theorize will have a healthy conversion to testosterone 4D-BOL promotes muscular density and hardness just after a few days of use. This rapid response seems related to its notable insulin mimetic activity, which is crucial to the anabolic effect of androgens.