Model 4481EFN12. 4x4" size for use with matte box. This 4 x 4" Tiffen Combination 81EF/ND Filter blends both an amber light-balancing 81EF and a 1.2 neutral density filter. The ND filtration provides a 4-stop exposure reduction for darkening the entire image in order to photograph with a wider aperture or slower shutter speed than normally required.