The bow tie is a men's necktie popularly worn with formal attire, such as suits or inner jackets. It consists of a ribbon of fabric tied around the collar in a symmetrical manner such that the two opposite ends form loops. Ready-tied bow ties are available, in which the distinctive bow is sewn into shape and the band around the neck incorporates a clip. Some "clip-ons" dispense with the band altogether, instead clipping to the collar. The traditional bow tie, consisting of a strip of cloth one must tie, may be known as a "self-tie" bow tie to distinguish it. Bow ties may be made of silk, polyester, cotton, or a mixture of fabrics. Some fabrics (e.g., wool) are much less common for bow ties than for ordinary neckties.