A perfect blend of four testosterone compounds. The four different testosterone esters provide for different half lives. Esterization of the testosterone molecules provides for a sustained (but non-linear) release of testosterone from the injection depot into the blood plasma.

While the intention of the mixed testosterone esters in Sustaplex is to provide more stable serum testosterone levels, the long-ester testosterones, such as testosterone cypionate or testosterone decanoate, provide more stable serum testosterone levels.

Sustos is the most popular testosterone blend product among those that use anabolic steroids for muscle building purposes.