Halotestin is an androgen. It works by stimulating normal growth and development of the male sex organs and maintaining normal secondary sex characteristics.
Where it is basically a one-trick-wonder used in the final weeks before a contest to harden up an already lean physique and give the user some added aggression during the final calorie depleted workouts before a contest. Halo has no estrogenic activity, and thus will not cause any kind of water retention or most of the bad effects associated with estrogen. It is however hepatoxic (liver toxic).