My recommendation, dont buy it to fly with, buy it as a replacement cover for the OEM bubble. I would instead buy a set of Tacos or Polar Pros, or just one filter that you would use regularly such as an ND4 or ND8.
This item a solid ND filter/gimbal bubble for the Mavic. I would not use this device because if you fly with it, or just keep it on for extended periods of time while your Mavic is running, you are preventing air from being circulated into the cooling fan intake behind the gimbal. This cooling intake needs to remain unobstructed or your internal components stand the chance of getting fried, in addition to the fact that you are making your cooling fan work very hard to suck air in through the intake.