This is a mounting ring to mount a filter to a Yukon Spartan Gen 1 Night vision device. It doesn't have a threading. You just push it into the objective and it should sit tight enough to stay there even with heavy use. The filter material has to be glued to the outer ring. This works well with infrared tranparent plastic or dark but transparent plastic. Camera filters are neither necessary nor useful because optical quality isn't needed with a gen 1 tube and those filters are to brittle for a night vision device. The inner ring is slightly bigger than the inner diameter of the rubber of the objective of the tube and does not interfere with focusing. It can be sanded smaller to fit into the objective if necessary. This device has 3 uses: Use the gen 1 tube during the day with a dark/black filter to "emulate" a gen 3 tube at lower price while using ambient light instead of an infrared illuminator. This way you have a greater range than with an infrared illuminator and almost the same user experience as if using an expensive gen 2 or gen 3 tube. Mount an infrared filter to the night vision device. This reduces glare and visual distractions through artificial light sources like cities, cars or flash lights a bit. A night vision device does not count as eye protection. Softairs and paintballs can get you blind and knock out your teeth.The filter film goes between the two rings. If you don't print out the second one it will get scratched soon. Stuff that works as a fitler includes window tinting film, acrylic glas or old photografic film.