Shallow lens hood designed for a Leica Summicron 50mm F2 lens. The hood protrudes just 12mm ahead of the lens filter thread. It can be used with or without a standard 39mm 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. This hood will provide close or equal shading to the original hood. It will also fit 90mm lenses (f2.8 or f4) with 39mm thread with or without a filter mounted. It should also fit Canon 50mm lenses that take a 40mm filter without a filter mounted, but I have not tested this. 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.