We review hundreds of products a month. Here are the 10 absolute best our editors tested this week.

Drunk Elephant’s C-Firma Fresh Day Serum is a high-quality, highly effective alternative. We loved it for all sorts of reasons. After six weeks of twice-daily use, our tester found that it both lightened dark spots, noticeably tightened her skin and consistently gave her complexion a pretty, brighter glow. But what makes C-Firma superior to nearly any competitor we tested was the unique way it’s packaged: The formula arrives in two parts — a liquid serum along with an accompanying vial of pristine vitamin C powder. You mix the two just before your first use, maximizing the stability of the vitamin C molecules and thus ensuring freshness. Once mixed, the product remains potent for three to six months, depending how you store it (i.e., preferably in a cool, dark place, like a cabinet). 

And there’s more to love: C-Firma contains ferulic acid and vitamin E, which boost its efficacy. It comes in an easy-to-use/easy-to-travel bottle with a convertible pump. It has a pleasant, mild, citrusy scent. It’s lightweight and absorbs quickly, though the texture may feel a bit a sticky for some. Finally, it’s potent — it may even sting your skin a bit.  

As compared to Skinceuticals C E Ferulic, Drunk Elephant’s C-Firma gains points for being both cruelty-free and free from a foul odor (C E Ferulic has a deeply unpleasant scent). While many beauty editors will tell you that C E Ferulic is the only vitamin C game in town, keep in mind that it’s also $182 to $285 for just one ounce, making it inaccessible for most bank-account-having humans, at least for long-term use. 

At $74, C-Firma is not exactly a steal, but the formula (plus the effect on your skin) is top-notch. My first bottle lasted four months with twice-daily use, so a little goes a long way.  

Read more about our testing of the best vitamin C serums.