This Biotin with Selenium & Zinc from Natural Elements is really useful. Great for when hair feels weak or starts falling out more than usual. Helps a lot with brittle nails that keep breaking. Also good for skin, especially when dealing with breakouts or dullness. Perfect for anyone who styles hair often with heat or dyes it a lot. Useful during stressful times or when diet isn't the best. One bottle lasts a whole year.