This K&F CONCEPT ND2-400 ND Filter reduce the light from 1 to 9 f-stops. Made by Completed Professional Optical Glasses, with double-side multilayer blue coating to help repel water. ND filters are good for rivers, waterfalls, and other bodies of water, especially under bright light. The longer exposure times allows for smoother water movements, shallower depth of field, and blurred motion. The filter frame is only 7.3mm, and super lightweight CNC ring used in construction prevents adverse effect.