You gotta be careful with Letro. Its wicked strong. The problem with letro is that its near impossible to find the right dose to combat your sides. So you either dont use enough and get sides, or you use too much and, at the very least, kill your sex drive. And if you use too much, you can hinder your gains pretty good.
Letrozole kills ALL the estrogen, but you need atleast some for the sex drive.
So, like halfy said, use adex, or use aromasin at 10mg/ed. If its for tren gyno you might wanna pick up some dostinex. When it comes to gyno from tren...letrozole will only kill the inflammation. Good luck bro
Chris