Cast Bore flutes are instruments that have a wooden body, but the bore of the instrument is cast into the wood, using a special Resin. There are a lot of advantages:
The bore is very stable and not affected by moisture. Compared to other plastic flutes made from ABS, Acetal, PVC or the likes they are much lighter. Wood that is not usually used for flutes can be used to make an instrument, a rather porous and light timber has even an advantage because the Resin can bond better with the wood by soaking deep into the grain of the wood and locking the resin tight to the wood.
Blow hole and noteholes are cast as well, so the blow or notehole chimney is made from Resin too. The Timber is well protected from moisture and the Cast Bore flute is practically maintenance free.