Hoya 77mm PROND 16 Neutral Density 4 Stop (1.2) ND Filter Exclusive Hoya ACCU-ND technology ensures accurate color balance when switching between ProND filters Filter provides "X" amount of neutral density stops (depending on the filter you can insert X-see press release) Super high quality "Hoya Clear" optical glass Assembled using a one-piece aluminum frame creating a rigid, durable, but lightweight filter Perfect for Still and Video applications