It is a personal preference which brand to use. When I used it Oxypowder was the first one out with capsules but now colosan has them too. I think there is another brand Max 007 (if I remember right).
Do read the websites so you understand how they work. The magnesium is only used as a carrier for the oxygen. It dissolves the solid fecal matter and when your intestines are clean the oxygen will be absorbed by the body. It is also beneficial for the intestinal flora.
Just to be safe read up on it, for me this is all several years ago.