I love this product. My hair dresser recommended it a few years ago. It is one of the best products I have used to prevent frizz. It doesn't take much and also adds a nice shine. I live in a damp area on the coast so this product is essential.
This stuff is pretty magical- use sparingly, however! Smells great, be sure to use a dime sized (or smaller) drop in your hand, run it all over your hands, and then run your fingers through the frizzy/dry area. It's potent, but that's the point. I've had one (very small) bottle last me for years. If you have trouble with frizz or dryness, give this stuff a shot.
I have tried several similar products and have found this to be the best. It use it after drying my hair but before straightening, and it reduces damage and adds shine. It is a heavy serum but is not greasy. I love it!