Shallow lens hood designed for a Jupiter 8 50mm F2 lens (late version). The hood protrudes just 12mm ahead of the lens filter thread. It can be used with or without a standard 40.5mm filter mounted. The 42mm outer dimension of the lens filter thread is gripped tightly by the flexible plastic of the hood. The tight sizing of the opening maximizes the shading of the front element while minimizing viewfinder blockage. The two aperture marks should line up with the two marks on the lens. A notch out makes it easier to adjust the aperture. NOTE: This hood attaches with friction, and will initially be very tight fitting. The grip pads can be gently scraped with a blade, to get a perfect fit. If after frequently taking it on and off, the fit becomes loose, some rubber cement can be dotted to the grip pads. Let it dry, and it will grip nicely again.