Letro is so powerful it's crazy. Sometimes I don't use anything, just keep Letro on hand. If I start feeling any gyno symptoms three days of Letro and it's gone completely. I don't know about using it through an entire cycle as your main gyno protector. It can destroy your estrogen so easily. You would need constant bloods. I know for a fact that high estrogen and high test equal more gains than just high test and super low estrogen. Need to keep Estero under control but you don't want it too low. Usually what I'll do is use either 10 MG of noveldex(which is not an ai so your Estero can still go high) with Letro on hand or proviron (which does act like an ai, eliminates estrogen) and again keep Letro there just in case. Personally, if it's a regular cycle, not precontest I mean, I would always start with 10-20mg noveldex only. That will block gyno but will not inhibit estrogen production. Like I said, it's just been my experience that a high Estro, high test environment in your body will allow the most growth. But you need to monitor it because the noveldex will block gyno but that doesn't mean your estrogen isn't through the roof. If your Estro is too high it can cause other problems. That's where you can add some arimidex or some other ai(I wouldn't recommend Letro it's just too strong). But I'm talking if your estrogen levels get to a very, very high number. I've tried test and other things with an ai and the results I got just were never as good as using noveldex and keeping an eye on it.