The Fabric Lens Donut from Tilta, also referred to as "Nun's Knickers", attaches directly to either the MB-T03 or MB-T05 matte box and is used to prevent light from leaking around the lens from behind the camera and degrading your image. The fabric donut can be used with lenses with an outside front diameter between 90 and 100mm. It is flexible, allowing you to work with lenses that change length when you focus or zoom without sacrificing the light-blocking effect. The donut slips around the front of your lens, and the integrated elastic band snugs it tight.