This is what we found on Wikipedia regarding the Kawala:

The kāwālā (Arabic: كاوالا‎ orكولة‎; also called salamiya,سلامية‎) is an end-blown cane flute used in Arabic music. It is similar to the ney but has six finger holes, while the ney has seven (including one in the back). The kawala comes in up to nine different sizes, according to the maqam.

Though very similar to the ney, a highly popular flute in traditional Middle Eastern music, the kawala does not have a hole in the back as the ney does. The kawala has the fundamental tonal structure customary among the Egyptian folk music community, and the basis for many folk melodies, instrumental or vocal.

The kawala is hollow and has four knots, with six fingerholes in a straight line along it. The instrument has up to nine different sizes, according to the scale required in a musical composition. Most often played today at religious festivals and weddings, it has its origin as a shepherds tool, used to guide their flock. For this reason the seems to assist in any musical composition that contains a “call-and-response” sequence.