Neewer Plastic DSLR Matte Box C1 for 15mm Rail Rod Support Follow Focus System mattebox designed for most DV cameras with wide angle lenses Matte box is a device used on the end of a lens to block the sun or other light source to prevent glare, which functions as that of lens hood. matte box is also be used to hold glass or plastic filters in place in front of the lens.It works with standard 15mm rail rod support systems, and fits lens from 43mm to 77mm sizes.(others do not fit.) This Matte Box could be adjusted the height (up to 45mm) according to the lens of camera on the rail rod system