Copper wound and Nylon wound nylon silk strings. 180 cm (71 inches) long. This set is made to fit the OUDX-A, Unadorned Eqpyptian oud only. `3 Pyramids` brand superior oud string set includes. 7 strings in 5 envelopes. Envelope 1: 2 strings .035 inches; Envelope 2: 2 strings .042 inches; Envelope 3: 1 string copper or bronze wound, .034; Envelope 4: 1 string copper or bronze wound, .036; Envelope 5: 1 string copper or bronze, .038