Leica's new line of neutral density filters are designed to reduce the amount of light coming through the lens by 4 stops. This allows you to significantly lengthen shutter speeds, experiment with motion blur and, for example, soften the motion of flowing water or clouds. It also makes moving persons or vehicles vanish from the scene when shooting with longer exposure times.
Alternatively, these filters allow you to shoot at wide open aperture in strong lighting conditions when otherwise the camera's fastest shutter speed would be exceeded resulting in an overexposed image. They are manufactured to the same optical standards and with the same aluminum used in Leica M lenses.
The filters are multicoated high grade optical glass to reduce internal reflections, and are lighter than their predecessors thanks to aluminum versus brass construction. Each filter includes a 2 year Leica warranty and protective plastic case.