For people, who used this on their cat?

Someone on YA's told me that this produt, shed - stop cats dietary supplement, that will help the cat not to shed fur, how does it work, and does it really work, is it safe for my two cats, and do I have to buy it at the vet, or can I buy it at any pet store. Cause I never like to buy things on the net, cause I think it's a scam. Have you used this on your cats,. and did it work for you, thanks, and how good does it work