To hear dermatologists tell it, if you’ve ever walked outside, your skin would be better for using a vitamin C serum. Years of sun exposure leads to free radicals, which over time make for skin that looks dull, uneven, tired, and generally not its best. Regularly using vitamin C, which is full of antioxidants (the trick to neutralizing free radicals), gives your skin a brighter, lit-from-within glow with good health. Seems like a no-brainer to use, no? The only downside is that historically vitamin C serums didn’t run cheap, and people would pay up because it was worth it. But thanks to Amazon, they’re both effective and affordable—almost suspiciously so. Given the shady sellers that can lurk online, it’s tough to tell which are legit. So Glamour‘s editors read the reviews, weighed the positives, and tested Amazon’s most-reviewed, reasonably priced, and generally beloved serums to find which ones deliver. Read on to shop our new go-tos.