They make nests out of grasses, feathers, and muskox wool (qiviut). Mechanical carding can cause breakage and weaken and roughen the qiviut. The raw, cleaned qiviut is spun and then the yarn is washed. An adult muskox can produce of qiviut a year. This lends itself to combing the qiviut from the animal in a single large sheet. Exotic fibers, such as silk, bamboo, yak and qiviut are growing in popularity as well. It is a knitting cooperative that works with qiviut and is still in operation today. Wild muskoxen have qiviut fibers approximately 18 micrometres in diameter. Qiviut is the fine underwool of the muskox. After dehairing, the qiviut may be cleaned again, if necessary. Qiviut is the fine inner wool of the muskox. The wool, qiviut, is highly prized for its softness, length, and insulation value. Qiviut is stronger and warmer than sheep's wool, and softer than cashmere wool.