I also use Hyaluronic acid and natural rose hip seed oil (organic retinol) in my serum and its awesome. The ultra great l-ascorbic is so g=difficult to find locally. I obtained 90g for 27 USD (shipping and delivery and all) little bit expensive but it surely goes a good distance. https://7figurebm.com/how-to-make-vitamin-c-serum-from-orange-peel/