My daughter has extremely thick and curly hair, especially now that she's a teenager. The only reason I didn't give it the full 5 stars is because I don't know how long it will last. She's only had it for about 4 weeks, and it's wonderful. She plays sports, and doesn't get the little fuzzies around her face after playing outside. Also, she doesn't have to use the straight iron every morning, which she used to do, so I think her hair will be healthier, and she doesn't spend so much time on her hair anymore!. Because her hair is long and thick, four ounces was barely enough to cover all her hair. Her hair is halfway down her back. I think 6oz would be best for her. The fumnes are rough while drying her hair, so we did this on the back balcony to cut down on the fumes. It took us 3 1/2 hours for the whole process.