Picks fall into 3 general categories - flatpicks, thumbpicks and fingerpicks. Flatpicks are also referred to as a plectrum and are generally in the shape of a triangle, and can range from an acute isosceles triangle to a nearly round shape. Materials range from plastic, rubber, felt, tortoiseshell, metal and even stone. Flatpicks are also available in a large variety of thicknesses and colors. Thumbpicks and fingerpicks are usually made of plastic or metal and attach to the finger or thumber, rather than being gripped like a flatpick.