I have both the polar pro and the freewell variable. I bought the freewell because I thought that it would be more convenient than swapping the polar pro's depending on the lighting, WRONG! The freewell works OK but it is heavier than the polar pro's and the camera drops face down when attached, It does not cause a problem when the gimbal is powered though. The main problem with the freewell is that it is wider and the gimbal guard does not fit on the gimbal with it attached, so i was back to taking it off and on like the polar pro's. According to other experts (I'm not) the fixed filters generally are better optically than the variable filters.