A simple, reliable solution for mounting 4.5" round filters to the Angenieux 25-250mm T3.9 zoom which has a 108.5mm front. It attaches to the front of the lens via a 108.5mm thread. The outside diameter is a clean 125mm surface for mounting clamp-on accessories to. It also provides a 4.5" filter thread for 4.5" filter retaining ring holders. Important to note: The front of the Angenieux 25-250mm T3.9 zoom rotates, so extra precaution should be taken when selecting filters. Circular polarizers will work fine, but linear polarizers will not, for instance.