letro for me, 1 bottle will last forever. i use aromasin, nolva, and hcg for pct. my former lifting partner like adex- says it was easier on his system. the very small amount that i use of the letro doesn't kill my estro. but like i said, i use it very sparingly, and only when i have symptoms of elevated estrogen. which is how you should use ai's anyway IMO.