The Biolage ColorLast Acidic Milk Rinse is a product designed to help maintain the vibrancy of color-treated hair. It comes in a 16.9 fl.oz bottle and serves as a conditioner or rinse-out treatment. The acidic formula helps to seal the hair cuticle, which can enhance the longevity of hair color by preventing fading. This rinse also works to detangle hair, leaving it smooth and shiny without weighing it down. It's typically used after shampooing and is suitable for color-treated hair types.