All flutes are also equipped with the new "Performance Flute Plug" in the headjoint crown assembly. Normally, this plug is made mainly from cork. However, cork eventually compresses and can be affected by climate issues. The new Performance plug in all Spirit models is made from Delrin (a hard synthetic) that is held in place using a double "O-Ring" configuration giving the headjoint assembly increased stability in any climate and moisture condition. While we will not comment on whether or not there is a sound difference due to the plug, we still do like the design simply from a maintenance and length of life concept. This plug will last much longer than traditional cork plugs that need to be replaced every 2 years or so.