Cirrus clous are characterized by thin, wisplike strands, often accompanied by tufts, leading to their common (non-standard) name of 'mare's tail'. Sometimes these brownish clouds are so extensive that they are virtually indistinguishable from one another, forming a veil or sheet called "cirrostratus". Sometimes convection at high altitudes produces another form of cirrus called "cirrocumulus", a pattern of small cloud tufts which include droplets of supercooled water.