There are some other popular vitamin C serums, some of which also include Vitamin E and Ferulic Acid. Skinceuticals, Drunk Elephant, Derma Doctor, Paulas Choice, to name a few but the price is generally higher, although the product is not necessarily a lot better. Have a look here for comparisons https://www.health.com/beauty/vitamin-c-serum

I've also used the skinceuticals CE ferulic, but that was just a bit too pricey. This smells better too and doesn't get old as quickly- you know where the Vit C oxidises? I think this is just as good at making my skin look just fabulous! Read here for a super guide on the best competitors with similar products https://simpleskincarescience.com/best-vitamin-c-serums-ascorbic-acid/