The Ice ND10000 is a 16.5-stop neutral density filter designed to photograph the sun. You can use it for non-sun photography, of course, but if you are going to use it for the sun stuff, please read the BIG WARNING down below. For lenses with a 77mm filter thread.

BIG WARNING: Do not use this filter to look directly at the sun. It is designed to protect your camera's sensor, but it is will not protect your eyes. If you look at the sun through this filter, you will permanently damage your eyesight. Do not use this filter on your camera if it has an optical viewfinder, because that is basically the same thing as looking at the sun. This filter should be used in Live View mode only to prevent permanent eye damage.