This is a 1/2 oz bottle of neutral black Spot-All Liquid B&W Retouching Dye from Marshall Retouching. Spot-All can be applied to most black and white films, as well photographic papers. It is a liquid that dries rapidly to eliminate unsightly white spots generally caused by dust on the photographic material. Typically, a fine point brush is used for application. Neutral black can not only be mixed with water, but with other colors of Spot-All. The bottle cap serves as an eye dropper.