Some will tell you letro, aromasine, or armidex. Others will say AIFM. I personally have not tried AIFM but I will shortly. If AIFM proves to work just as good or better I might make the switch. I have used letro for over 3mos in the past w no notable problems. I dont know how my lipids and such were. I think I overheard aromasin has some benefits. Im sure Mr. X, Marco, or utler will pop in on this one.