The individual joints of the drill pipe are called a “Single”. The “Singles” are then further identified by their length. Specifically, the lengths are identified using a three-part API length range, so the lengths will be classified as a one, two or a three. The most common length of drill pipes is range two. This is important, because when looking to determine the depth of drilling, you need to exactly take into account the length of the drill string (including the drill pipe)