Testosterone enanthate is a modified form of testosterone, where a carboxylic acid ester (enanthoic acid) has been attached to the 17-beta hydroxyl group. Esterfied forms of testosterone are less polar free testosterone, and are absorbed more slowly from the area of injection. Once in the bloodstream, the ester is removed to yield free (active) testosterone. Esterified forms of testosterone are designed to prolong the window of therapeutic effect following administration, allowing for a less frequent injection schedule compared to injections of free (unesterified) steroid. The half-life of testosterone enanthate is approximately 8 days after injection. Testosterone enanthate is highly favored by athletes to promote strong increases in muscle mass and strength. It is usually incorporated into bulking phases of training, when added water retention will be of little consequence, users are generally more concerned with raw mass then definition. Some do incorporate it into cutting cycles as well, but typically in lower doses and usually accompanied by an aromatase inhibitor to keep estrogen levels under control. Testosterone enanthate is effective on its own but many do stack it with other anabolic/androgenic steroids to tailor the desired effect.