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High clouds are found from between 16,500 and 45,000 feet (5,000 to 13,700 meters) and include (from highest to lowest) cirrus, cirrocumulus, and cirrostratus. A cirrus cloud appears in delicate, feather-like bands, sometimes in tufts, and is usually white. Cirrocumulus clouds look like very small round balls or flakes. Sometimes cirrocumulus clouds form the pattern of what is called a "buttermilk" or "mackerel" sky. Cirrostratus clouds sometimes form tangled webs or thin whitish sheets. When cirrostratus clouds cover the sky, a large ring or halo is sometimes seen around the sun or moon. This is caused by the bending of rays of sunlight or moonlight as they pass through the ice particles which make up the clouds.