Hair masks are a little like face masks they help to revive and nourish dry and damaged hair. To use you simply leave in hair for the recommended time on the packaging and then rinse.
I found this macadamia oil extract hair mask (see image bellow) in a shop called family bargains. Family bargains is a shop that sells food to make up to garden goods etc and they are literally bargains. I found this hair mask for only 99p and it is a very good size and a very good product. So if you haven't done so already pop down to family bargains and have a look around.