Vitamin C in the form of basic ascorbic acid powder which is the best delivery system as it can be mixed with serums or moisturizers. What's no to love? I also use it in my hydration and exfoliation masques for that extra oomph! And it's price point is really inexpensive given that it's the real deal, not a cream or gel that lists water as it's first ingredient. With the powder you get all the power of vitamin C. I'm happy with the results.
A great way for anyone with sensitive skin to use Vitamin C without the usual irritation. Start with a small amount mixed in your palm with a liquid or cream and applied. (Can test first overnight in the crook of an elbow.) Build up the amount of powder slowly. Be patient. Daily application on age spots will see them diminished. Applied to the whole face Vitamin C will brighten your skin and eventually even its tone.