Testosterone is a hormone produced predominantly in the testes of males. It is responsible for nearly all of the sexual traits in males. This specific version is Testosterone with the Phenylpropionate ester attached. Testosterone Phenylpropionate has an active life of 4-5 day. Release time-wise, it is directly in the middle of the Propionate (short) and Cypionate (long) versions of Testosterone. It is recommended to inject Testosterone Phenylpropionate two times per week, although many prefer every third day.