Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2236519.
This adapter allows a 24mm CPL (Circular Polarising) filter to be fitted to the Koonlung K1S Dashcam. This can help to significantly reduce reflections from the windscreen and dashboard. It's designed to accept the commonly available 24mm CPL filter available for the "Mini 0806 Camera", for example: https://www.google.co.uk/#q=24mm+cpl+0806 The CPL filter is intended to be a fairly tight fit in the adapter. To secure the adapter to the camera, there's a recess included for an M3 nut, and M3 screw. For this I used an M3x6 Nylon screw and nut, to avoid damaging the camera.
Note that 24mm is the diameter of the filter glass, the outer diameter of the CPL filter body is actually 26mm and it's about 4.15mm thick.
As the filter is rotated to the correct angle, most of the reflections should be eliminated, then you can tighten the screw to secure it (taking care not to over tighten).