The Cokin 121M Graduated ND4 filter for Samyang SFH-14 is a is a graduated neutral density ND4 filter (Grad ND4). This gives progressive graduation from the middle to the top of the filter to darken top, or bottom of the frame if used upside down etc. Dedicated for use with the Samyang SFH-14 filter holder with the Samyang 14mm lenses.
Further information: In total there are three Cokin filters available 154, 121M and 123S (each sold separately) which have been specially developed for the Samyang SFH-14 filter holder (sold separately). The Cokin filters are a large 161 x 139 x 3mm size. The SFH-14 is the filter holder for the Samyang 14mm lenses, enabling filters to be attached to these ultra-wide angle lenses.