A genuine Duclos Lenses accessory, the 136-138mm clamps confidently onto the front of any lens with a 136mm front ring such as the Angenieux 25-250mm HR, 17-80 Optimo, or 180mm Cooke S4. Place 138mm Round Filters into the front and thread in the retaining ring to secure your filter. 138mm Retaining Ring not included.