B+W 66-1066168 77mm ND 1.8-64X Neutral Density Filter (106M) with Multi-Resistant Coating (MRC) 1.8 ND - 6 f-stops - transmits 1.65% of the light from the Original scene Filter Factor = 64x Allows creative use of larger apertures for shallow Depth of field or slower shutter speeds to capture motion Blur MRC multi resistant coating - anti-reflection and easy-to-clean coating This filter uses our standard B+W F-Pro filter mount, which has a front accessory thread and is made of Brass.