Catalase 10,000 works
This product works for me. I'm a 68 female and have been using this product for over 8 years. It maintains my natural color, because all the new hairs that grow are in my natural color. I have very few scattered gray hairs and I can not say for sure if it reverses my few gray hairs but I do believe it prevents new gray hairs from growing. My husband who is a 73 physician/scientist, also uses it, and when I trim his hair/beard, I see lots of new dark brown hairs. (Research on Pub Med medical articles show that Catalase helps protect melanocytes from peroxide damage that causes gray hair). Look it up for yourself. It's foolish to expect short term results.
It's all about keeping what you already have a little longer.