I used the C products a few years ago and honestly don't know why I stopped. All three products work so well together to firm and clear your skin of all those unwanted age and sun spots. The eye serum could be a little thicker but it still works well. The Vitamin C Ester Serum is wonderful and smell so good. However, the manic happens when you add the Vitamin C Ester 15, it firms my skin better than any product in the line!! I have been using the C line at night and rotate my other products in as needed. I will keep buying this line!