Many advanced users stack several compounds in order to get maximum results from their cycle. Normally when your stacking these types of products its best to use single compounds instead of premixed stacks. The problem with using a premixed stack is you may get more of one compound than you want. Most of these products have sweet spots. Lets use h-drol for an example according to many of the forums out there 75mg is the sweet spot for this compound. Now lets say you have a halodrol product that is mixed with 10mg of Methylstenbolone. In order to get the proper amount of hdrol you will get more than the recommended dose of M-sten.