Aromasin is an Aromatase Inhibitor which stops the conversion of Androgens into estrogen by disabling the aromatase enzyme once binded to it. It basically prevents the chance of developing breast tissue while on cycle (cycle dependent).
24 - 36 hours.
2 Weeks from your last tablet - all traces will be out of your system for the purpose of drug testing/urine/blood samples.
20mg per day or every other day.