Masteron is a highly androgenic injectable steroid that is derived from DHT (dihydrotestosterone). DHT does not aromatize to estrogen (and in fact may combat estrogenic sides), and as a result, there was no noted water retention during administration nor gynocomastia. Masteron is almost exclusively used during the last 4-5 weeks before a bodybuilding show at a dose of 100-mg every second day. Additionally, according to available literature, Masteron is not much of a mass drug, and it's always used for cutting, from what I've seen reported. Masteron has a receptor binding ability above that of testosterone, due to it's being DHT-derived, which should impart lypolytic (fat-burning) effects above that of testosterone, and also give it a nice strength building component.
Injectable steroids are injected into muscle tissue, not into the veins. They are slowly released from the muscles into the rest of the body, and may be detectable for months after last use. Injectable steroids can be oil-based or water-based. Injectable anabolic steroids which are oil-based have longer half-life than water-based steroids. Both steroid types have much longer half-lives than oral anabolic steroids. And this is proving to be a drawback for injectables as they have high probability of being detected in drug screening since their clearance times tend to be longer than orals. Athletes resolve this problem by using injectable testosterone early in the cycle then switch to orals when approaching the end of the cycle and drug testing is imminent.