sust is a steriod compound composed of 4 diferents forms of test. test propionate, test phenylpropionate,testisocaproate, and test decanate. sust, milligram for milligram, has a better effect than test enth, test cyp, and test prop. the effect of the four test is time released. so that sust goes rapidly into the system and remain active for several week. if you want more info on sust than ask me i can answer all your questions.