Testosterone Enanthate 2500mg x 1 vial (10ml)(250mg/ml) Testosterone-Propionate is simply testosterone; compared to other forms there is no difference in-terms of mode of action as the nature of the testosterone hormone is the same in each form in-terms of benefits and function. Like all testosterone forms, Testosterone-Propionate is defined by the ester that is attached, as is the case with all forms or in some cases defined by the lack of ester attached, as can be the case in certain instances. To fully understand the compound we need only understand two things; the active hormone itself and then the ester and how it affects its mode of action in-terms of time release and active duration. While all testosterone forms can provide the same benefits, Testosterone-Propionate functions based on the ester attached; in this case the Propionate ester. A very short ester, as such milligram for milligram Testosterone-Propionate is more powerful than many other common forms. For example, another common form of testosterone is that of Testosterone-Cypionate; 100mg of Testosterone-Cypionate will yield approximately 70mg of active testosterone; however, as the Propionate ester takes up less mass in the compound 100mg of Testosterone-Propionate will yield approximately 83mg of testosterone. As a short ester based testosterone Testosterone-Propionate carries a half-life of approximately 4 days; the shortest half-life of all common ester based testosterones. As such, once administered the active hormone enters the blood stream and becomes active in full capacity very quickly but it also dissipates just as fast. For example, 100mg of Testosterone-Propionate administered on day one will fall to 50mg by day 4 and 25mg by day 8 and so on. Conversely, so that you may understand the significance, 100mg of Testosterone-Cypionate administered on day one will fall to 50mg but not until day 12 post injection. For this reason, in order to maintain stable and peak levels of the hormone in the body we must necessarily administer the hormone once every 3 days with every other day being optimal.