Sōmen (素麺, Sōmen) are very thin, white Japanese noodles made of wheat flour. The noodles are usually served cold and are less than 1.3 mm in diameter. The distinction between sōmen and the next thicker wheat noodles hiyamugi and even thicker Japanese wheat noodles udon is that sōmen is stretched while hiyamugi and udon are cut.