Dog joint supplement which seems to be good

I found this on Amazon (cheapest on the internet):
http://www.amazon.com/Synovi-G3-Soft-Chews-120/dp/B000ALI5H4/ref=pd_bbs_sr_2/103-7227992-5138250?ie=UTF8&s=home-garden&qid=1190477723&sr=8-2

It has many good reviews:

http://www.valleyvet.com/ct_reviews_view.html?groupguid=e1f67e41-e7e4-4262-a19f-0a183b2fafa2

I just bought 2 for my dogs although they don't have joint problem and are still young(3, 4 years old). I think it might be better to start earlier than later.