1. optical glass, precision polished and polished for high definition imaging 2. multi-layer nano-coating process, giving the lens high quality waterproof, oil-proof, dirt-proof and scratch-proof performance 3. Aircraft aluminium frame, laser engraved logo, dark grey frame to prevent ghosting 4. anti- gear design, knurled pattern on the top and bottom of the frame, easy to install and remove 5. installation without damaging the lens and changing the filter at any time so that you don't miss a great moment The lens is made by nano-coating process, the colour presented by the lens is different under sunlight and light. Cautions: 1. only UV filters transmit 98.5% of light, /ND filters cannot be expressed in terms of light transmission, 2. Installation and disassembly will touch the lenses and leave , use a cleaning cloth to wipe the lenses. Applicable models:for Action 4 Type:ND8/ND16/ND32/ND64 Colour:Dark Gray Material:Aluminum alloy + optical glass Package Contents: 4 x Filter 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. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.