The Lee SW150 Neutral Density (ND) Grad Medium Filter Set contains three 150 x 170mm graduated resin filters (0.3, 0.6 and 0.9) that enable the photographer to adjust exposure (by 1, 2, and 3 stops) over part of the photograph without affecting the colour balance. These ND grads feature a medium transition from dark to light and are ideal for use when elements of the scene protrude into the sky, be that the rooftops of buildings or the peaks of mountains. The nature of the transition between coated and uncoated areas of the filter means that the sky can be filtered with minimal impact on the land beneath it. The Lee SW150 Filter Holder and Adapter Ring are required, not included.