The Brilliant² 4x5.65/138mm Variable Neutral Density Filter is designed to fit in 4x5.65" matte boxes, occupying 2 slots in the matte box. It is constructed using two 138mm linear polarizers. One of the polarizers rotates and the other is fixed. The Brilliant² Variable ND provides ND values between ND 0.6 (2 Stops) and ND 2.1 (8 Stops).