TrueCam M5 WiFi / M7 GPS Double magnetic CPL filter A special polarisation filter prevents unwanted glare effects, such as reflections on the dashboard in the windscreen. The magnetic mounting makes operation easy. The Polarizing Filter is an excellent addition to your car camera, as it reduces glare and the negative effects of sunlight that would otherwise degrade the quality of the picture, while at the same time reducing overexposure of the sky. Most importantly, it significantly reduces the reflection of the car interior on the windscreen.