They are awful since many of them contain large % of speed in it. That in itself can wreak havac on your liver and other functioning organs. Steer clear from it. I don't agree with monkeying with the thyroid, that can lead to irreversible damage. A friend of mine was using all sorts of these fat burners (legal/illegal) and wrestled DI college and could have gone to the World Cup and wrestled but he needed immediate surgery on his thyroid or he could have died. That is a true story. He was my best friend, wrestling training partner since mat rats all thru highschool. We still train but he'll tell you this kind of stuff can kill you. He was also using about 1g of eph a week along with phentermine and T3/T4/T5. Again just find a proven and safer alternative. I have some GP clen and Berlin CHemie t3 and I had to stop using them because I was dropping weight too fast and was shaking like a retard. Just uncomfortable. I think I'm done using clen and any Thyroid activators! My life is worth it to me