The K&F Concept 55mm HMC ND2-ND400 Variable C Series ND Camera Lens Filter is a versatile and affordable filter that allows you to control the amount of light entering your camera lens. It features a variable neutral density range from ND2 to ND400, which provides an adjustable light reduction of 1 to 8.6 stops. This means that you can use it to create long exposure effects in bright conditions, such as shooting waterfalls or cityscapes at sunrise or sunset. It can also be used to reduce the depth of field in your images, which can be helpful for portraiture or product photography.