Clenbuterol is most effective for two weeks only, and it is best stacked with T3. T3 is good for 5 weeks, pyramiding up, then down. 5 weeks on, 8 weeks off, take the clen the 2nd and third week. I personally have had good results with this. You will be kinda hyper and possibly shaking the first week of the clen..like taking ECA.