As the name describes, this is a silicone hood for your lens. It’s has a designed contort to seal around a window to cut out unwanted reflections. It comes in two sizes, One for 50-70mm lens and another for 70-90mm lens. Most of my lenses are on the larger side, so I opted for the 70-90mm version.
The large hood is 210mm wide and is designed to stretch over your lens to hold in place. You can even do this while the lens is mounted. Check the photo above.