I am in the military and needed a red filter for the flashlight for night use. I found some filters from my other lights and cut them to size. Then wrapped the tip of the light with cling-film and put the filter on top. After i formed Sugru around the tip of the light and the filter. I also used the knurled surface of the flashlight to texture the Sugru on the filter body. It worked so well I made a red and green filter! Scott, Canada