Hoya PRO-ND 77mm 4x Neutral Density Filter, 2 Stops (0.6) 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) Manufactured from 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