The most sellers on Ebay are cheap as their duduk seems to be, cannot be recommended, if you a serious about getting a good instrument by professional master and musician. I personally own several duduks made in Armenia and sold by ethnictune.com, which are really incredible in sound and the reeds, which is also very important are very high in quality and very well tuned.

See link here: https://ethnictune.com/shop/duduk-tenor-studio/