We created the Neutral Density Filter Twin Pack to enable Polaroid SX-70 shooters to use any Impossible 600 type film in their Polaroid SX-70 cameras. These reusable Neutral Density filters are easy to attach and detach. All you need to do is insert the filter on top of an Impossible 600 type film cartridge - it adjusts 600 type films to around 100 ASA, so they can be used with a Polaroid SX-70 camera. No changes are required for the camera itself. The Neutral Density Filter Twin Pack contains 2 reusable Neutral Density filters.