Proviron is first-generation anti-e. So is Teslac. So is Nolvadex. Since we have Nolvadex, Clomid, evista, arimidex, femara, and aromasin, we can pick and choose the appropriate anti-e for the situation and the individual. I prefer to use aromatase inhibitors DURING an aromatizing AAS cycle. These are arimidex, femara, and aromasin. The choice is based on availability, the individual's tendancy to develop estrogenic sides, and the dosing/frequency/type of aromatizing AAS used. If you do not know your response to aromatizing AAS, then choose one of the aromatase inhibitors and monitor your situation. You may need to change meds or lower AAS doses. I have found that those with BF% over 15 tend to aromatize more. The reason: the largest concentration the aromatase enzyme is found in adipose tissue.