The tiffen multi rotating tray mrt base unit with circular polariser kit allows the use and rotation of a 138mm circular polariser included and a 4x565 circular polariser included simultaneously when both filters are used together it can be used as a variable neutral density nd filter up to 6 stops or to produce warmcool colour effects the tray is ideal for matte boxes that come without a rotating filter stage or when a secondary rotating filter stage is required in a non rotatin