This is a 20ml bottle of Choroi's Flute Oil for our Pentatonic flutes.  According to the insert that comes with our Quinta Pentatonic Flute :  "...oil the flute regularly (at least once a month), both inside and out, and wipe inside with the swab after each use.  To oil inside the pipe, place some drops of oil on the swabbing paper at the tip of the swab.  In addition, place a drop of oil in the slit where you blow, whenever the wood in this area appears lighter in color."   Made from Lindseed Oil.