What is an ND (neutral density) filter? Also known as a neutral density filter, its function is to reduce the amount of light entering the lens, helping achieve better exposure in bright conditions. The neutral density filter plays an important role in achieving high-quality photography. Ultra-clear optical glass This ND filter is made from optical glass with double-sided multi-layer coating, which enhances light transmission and reduces reflectivity. It features low color cast, accurately restores colors, and improves image quality. Compatible with most mobile phones 7mm large opening fits over 99% of phone models without blocking the lens. How to use an ND filter on a mobile phone: 1. Secure your phone; slow shutter speeds require longer exposure times, so use of a tripod is recommended. 2. Attach the ND filter. 3. Open the cameras professional mode. 4. Set the ISO sensitivity to the lowest value. 5. Adjust the shutter speed to the desired setting and take the photo. Android: Most Android phones have a professional mode that allows adjustment of ISO and shutter speed. iPhone: It is recommended to download third-party camera apps such as Camera+, which allow control over ISO sensitivity, shutter speed, and white balance. Note: Please verify the product specifications to ensure this item meets your needs. Product design and packaging may be updated between batches, resulting in slight variations in appearance or color. These differences do not affect functionality. Color: Black Material: Aluminum Package Contents: 1 x ND2-400 (67mm) lens filter 1 x Lens cap 1 x Clip 1 x Storage bag Note: Light reflections and screen display differences may cause slight variations in the color shown in images compared to the actual product. Measurement error allowance is +/- 1-3 cm.