“For me, the 20mg work best. I use them at least 3-4 hours before activity and this seems to be the best window for me. I'm almost 50 and these things give me the stamina of a young man! I tried the 10mg and it was not as intense. I even tried using two 10mg pills to equal 20mg (to use up and not waste the few 10mg I had) and they still did not work as good as a single 20mg pill. Not sure why that is. I'll be sticking to 20mg.”