Alright lets look at the differences between Primo & Tren Ace. With Primobolan your looking at a very mild compound which isn't C17 alpha alkylated. The androgenic activity of Primo is considerably low, as well as its anabolic properties. Also it does not aromatize. So estrogen related side effects are no concern when running this compound. it is said to have a low impact on endogenous testosterone production; however we like to run Primo at doses of 800mg-1000mg/wk. And with that there can be a noted suppression of gonadotropin levels. With Primo you can expect nice slow and steady increase in quality lean mass (not as such D-bol or Abomb when I say MASS). With Tren your looking at a potent androgen that produces very STRONG anabolic activity. Trenbolone just like Primo also does not aromatize, so you will not gain any estrogen related side effects. Some side effect you will experience with it more than likely will be, added aggressiveness, insomnia,night sweats, and oily skin. Trenbolone acetate is a 19-nortestosterone derivative that offers a suppression stemming from the androgen action. So just as with the higher doses of Primo supression of gonadotropin levels will also take a hit. It does greatly and dramatically increase IGF-1 production in the body. IGF-1 affects every cell in the human body (hence why Tren is called "poor mans GH). Along with this Tren also promotes nitrogen retention, enhances proteins synthesis, and increases red blood cell count. In short terms, it will allow you to recover faster and be able to push through those grueling workouts. Common dosages of Tren are anywhere from 350mgs-800mgs/wk. Those are some simple differences between Primo & Tren. With that said Less side effects will come from Primo, but is a much weaker compound that must be ran at higher doses to achieve results. On the other hand Tren is a VERY STRONG compound with more profound side effects, but does bring promising results for those that can handle it.