This pulley is used for small motors with 2-mm shaft. The diameter of the bore (center hole) is 1.95 mm so that it can make a snug connection with 2-mm shafts.
Outside diameter is 18 mm and the diameter inside the groove is 16 mm. Overall thickness of the pulley (Width, near the center) is 6.3 mm. The belts (string or rubber bands) with thickness of 1 to 2 millimeters may be used with this pulley.
Sold in packs of 10.