I've been using the OST C 20 Original Pure Vitamin C20 Serum for about five months now. It does exactly what I want a vitamin C serum to do for a fair enough price. I only need to use three drops or so at a time and that's enough to cover my whole face. Which means that this product lasts for a fairly long while, despite coming in a small glass container.

My skin type: mid-twenties/mostly normal/dry cheeks/arid climate. Main skin concern: sun damage, whiteheads, dullness, slight redness in some places. Additional: preventative anti-aging.

Pros

- Goes on very smoothly.

- Lovely, light citrus scent.

- Performs well. My skin is noticeably brightened/smoothened the next morning when I've used this serum overnight. My slight forehead lines disappear too, which is nice.

- A thin layer of product is enough.

Cons

- It's drying. Once I ended up flaking after using this serum. Remember to moisturize x2 after using this if you're dry-skinned/dehydrated.

- Putting on more than a very thin layer may result in later products not absorbing as well.

In conclusion: 5 of 5 stars. This is a concentrated serum that performs admirably. Keeping it in the fridge ensures that it does not oxidize too quickly. Remember to check its color before usage - it should be clear to champagne-colored.

I would recommend this to:

- everybody, but especially normal-oily skinned people.

- people wanting a brightening/anti-aging product that produces visible results.