Velvet can be made from several different kinds of fibers, traditionally, the most expensive of which is silk. Much of the velvet sold today as "silk velvet" is actually a mix of rayon and silk. Velvet made entirely from silk is rare and usually has market prices of several hundred US dollars per yard. Cotton is also used to make velvet, though this often results in a less luxurious fabric. Velvet can also be made from fibers such as linen, mohair, and wool. A cloth made by the Kuba people of the Democratic Republic of Congo from raffia is often referred to as "Kuba velvet". More recently, synthetic velvets have been developed, mostly from polyester, nylon, viscose, acetate, and from either mixtures of different synthetics or from combined synthetics and natural fibers (for example viscose mixed with silk produces a very soft, reflective fabric). A small percentage of spandex is sometimes added to give the final material a certain amount of stretch (hence "stretch velvet").