I purchased the 500gm package. It appears to be a good value. I have not had any luck in having the results reported by Jonathan. My first day I only took 2-2.5gms twice. I noticed an increase in energy...but then crashed, redosed for the afternoon and crashed pretty hard that evening. I did not feel I had an increase in my mental abilities or focus. The second day, I upped the dosage to 3gms and did not crash and I don't know that I had and increase in mental abilities but I did notice an alertness and sharpness. The Third day I kept the dosage the same, no crash and still increased alertness. I think I will up the dosage tomorrow to see if I have an increase in focus and memory. Not giving up yet. I have not had any headaches. Any suggestions are welcome.