The MRC Box enables compensation for wind angle on rotating masts. It measures the angle and direction of mast rotation, enabling the pilot to steer and the system to display true and apparent wind information, which is corrected to allow for mast rotation. An electronic compass, such as the HPC, must also be fitted to any system using the MRC. The MRC weighs only 40 grams and both the unit and all direct connectors are waterproof.