This Cokin Z-Pro Series Hard-Edge Graduated Neutral Density Filter Kit contains three filters that can be used individually or in various combinations to improve the results of your landscape photography by preventing overexposure in specific areas of an image, such as bright skies, while allowing for a normal, unaffected exposure in the other regions of the image. The included filters consist of 100 x 150mm graduated neutral density filters that reduce the amount of light entering a lens by up to one, two, and three stops, respectively. Each filter is densest at the edge and tapers to clear by the middle, with a hard-edged line of transition between the dense and clear areas. A graduated neutral density filter with a hard-edged line of transition is useful for images which include defined horizon lines. Together, these filters provide a versatile solution for various lighting conditions. To allow these filters to be placed in front of a lens, a separately-available Cokin Z-Pro Series filter holder and a Cokin Z-Pro Series lens adapter ring are required. Each filter is made of durable, optical resin (CR39) and measures 1.6mm thick.