GNC sucks ass. It's just a crazy scheme to turn a profit by dangling an " easy way " to pass in front of a pot-smokers face. PAH!
Think about it. If it seems too good to be true ( like a 2 day detox for someone who is a DAILY smoker ) ... not probably -- it IS too good to be true.
No such thing as a free lunch, etc.
Do yourself a favor. Don't stop smoking. Substitute. I can't stress how much time and stress it saved me. Unless you have a month or more to detox, forget about it. Find a clean donor and let him/her do your business.

FUCK GNC! I'll second that Acoustic! Good luck. And happy puffing.