Testoviron 350 is a blend of two different products, namely testosterone with the propionate ester attached, and testosterone with the Enanthate ester attached. Confusingly, XT LABS , who produces this product, also has a pure testosterone Enanthate product of the same name. Testosterone is usually attached to an ester . These esters determines how long it takes your body to dispose of the testosterone, and propionate is the shortest ester commonly available with a testosterone base , whereas Enanthate is the longest generally available with a testosterone base. Within your body, there are enzymes, called esterases, which have the function of removing the ester from steroids, and leaving you with just the steroid molecule with the ester cleaved off. Depending on how heavy the ester chain is, that determines how long it takes the esterase to remove it. With this product, you have testosterone with a heavy chain as well as with a short chain.