And take note: reviewers say it’s comparable to the SkinCeuticals CE Ferulic serum (which, by the way, costs $182 for the full size!).

Promising review: “Magic potion. Where has this been all my life? This stuff is amazing! At 31, I’m trying to take better care of my skin because I notice that my face looks “tired”. I started using this and saw results right away. I apply it after washing/derma roller and follow up with moisturizer. My husband even noticed a difference after a week of use and said things like “your face glows”, “your face looks radiant”, “you look different, younger”, “whatever you do, it works”. In short, if you are looking for an anti-aging serum, stop looking and buy this.” —JDM

Promising review: “I should have started using this years ago! I’m in my mid 30’s and I’ve tried everything including much more expensive brands, Korean skincare, Japanese skincare, etc. but I’ve always struggled with breakouts and texture issues. This is by far the best vitamin C product I have ever tried. I have tried several serums with vitamin C in the past, but they always gave me breakouts or a slimy/grainy texture. This serum has a smooth texture, absorbs quickly, does not pill with other products, and has noticeably brightened my skin.” —Amazon customer

Buy it from Amazon for $21.41 (originally $37.36; also available in a smaller size – clip the $10 coupon to get this price)