To quote from a Leica brochure... "The Leica polarizer filter simply pivots 180 degrees to the 12:00 position above the camera. While looking directly through filter, the polarizer is rotated until the desired effect is achieved. Then the polarizer is swung (or pivoted) back to the closed position - which is exactly a 180 degree arc. Now the polarizer filter is front of the lens and doing its job. The simplicity is genius." Here is the link at B&H... Of course, this genius is priced in the Leica tradition $$$