The adapter ring is made of high quality anodized black aluminum(metal).
This 10-slots filter case can hold 37-82mm circular filter and cokin P series square filter.
The full ND filters(ND2, ND4, ND8, ND16)reduce the amount of light reaching the film without affecting the color. Can be used to enable slower shutter speeds.
The graduated ND filters(ND2, ND4, N8, ND16)are a MUST for digital users, because the digital sensor unlike film has very low exposure tolerance. Detail will be lost on both low and high light area. To correct this, you need graduated filters to balance it.