What is ND (neutral density filter)? Also called neutral density filter, its function is to reduce the entry of light when , Neutral density filter plays a very important role in a good photo. Ultra-clear optical glass - ND filter is made of optical glass material, double-sided multi-layer coating, which can enhance transmittance and reduce reflectivity. Low color cast, restore color, and improve image quality. Mainstream mobile phones can be used - 67mm large opening, suitable for more than 99% of models, without blocking the mobile phone lens. How to use ND filter on mobile phone: 1. Fix the mobile phone, slow shutter requires a longer exposure time, it is recommended to use a tripod 2. Add ND filter 3. Open the camera professional mode 4. Reduce the sensitivity to the lowest value 5. Adjust the shutter time to the appropriate position and click to Android: Most Android phones have professional modes, which can adjust IS0 and shutter speed. for : It is recommended to download the camera+ software, which can adjust sensitivity, shutter speed, self-balancing, etc. Note: Please check as much as possible to make sure the item is what you need. Tips:The product may be updated constantly ,Due To Different Batches, The Actual Product May Have Slight Differences Or Color Differences, Which Does Not Affect Use. Colour:Black Material:aluminum Package Contents: 1 * ND2-400 (67mm) lens 1 * lens cap 1 * clip 1 * storage bag Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.