The Bright Tangerine 114-110mm Threaded Adapter Ring is made specifically for the adapting lenses with a 110mm outer diameter to work with the Bright Tangerine 143mm Rubber Donut with 114mm Metal Threaded Ring. This adapter allows you to use your lens with a Bright Tangerine rod-mounted matte box with a 143mm rear opening and the rubber donut while maintaining a light tight seal. The adapter ring is made out of Delrin, which is an industry-standard material used for lens fronts and matte box donuts.