Triune: The three flanges help to keep the tube in perpendicular relationship to the eardrum

-3.0% perforation rate!
-Easy insertion with standard forceps!
-Soft angled flanges contour to the TM!
-Three flanges hold the tube perpendicular to the TM!
See: http://www.gracemedical.com/sites/488/uploaded/files/LIT0056_CID6021_Triune_Tube_Sales_Sheet.pdf