Just For Men Jet Black Color Shampoo targets only gray hair and replaces it with subtle tones that match your own natural color in 5 easy minutes. The ammonia-free formula lasts up to 6 weeks until the gray disappears. Just For Men Haircolor Jet Black Shampoo only takes five minutes as it targets and colors only gray hair, leaving your natural color intact. You won't get the dramatic color change you get with some women's hair colors. And once you apply Just For Men, you're done. You can shampoo as often as you want and treat your hair the way you always have. Just For Men lasts up to six weeks or from one haircut to the next. Just For Men Natural Real Black Color Shampoo targets only gray hair and replaces it with subtle tones that match your own natural color in 5 easy minutes. Ammonia-free formula lasts up to 6 weeks until gray disappears.