A donut is a lighting accessory designed to enhance the sharpness of gobo projections in Source Four ellipsoidal reflector spotlights. It fits into the color frame slot of Source Four fixtures and works by reducing the aperture size, which minimizes flare and stray light while improving the clarity of projected patterns. Commonly used with fixed lens models ranging from 19 to 50 degrees and Source Four Junior fixtures, the donut is fabricated from lightweight steel with a black powder-coated finish. Aperture sizes vary by model, with standard versions featuring a 3.25-inch center opening within a 6.25-inch outer diameter. While it may slightly reduce overall brightness, the improved image definition makes it a valuable tool for theatrical, studio, and event lighting applications.