【Variable ND Filter】K&F CONCEPT ND2-400 Filter reduces the light from 1 to 9 f-stops. 【Material】Made by Completed Professional Optical Glasses, with double-side multilayer blue coating to help repel water. 【Exposure Reduction】ND filters are good for rivers, waterfalls, and other bodies of water, especially under bright light. The longer exposure times allow for smoother water movements, shallower depth of field, and blurred motion. 【Ultra-Slim】The filter frame is only 7.3mm, and the super lightweight CNC ring used in construction prevents adverse effects. 【Note】This Filter kit is compatible with all 55mm lenses. Please verify your camera's lens thread size before ordering. Your camera's lens thread size will be marked somewhere on the lens barrel or printed underneath your lens cap. This number is always preceded by a "ø" (diameter) symbol.