The King F9 SpeedBack irons are a combination of tungsten weighting and innovative shaping to deliver the most powerful and stable COBRA iron. In addition, features a 3 piece multi-material medallion design that contains aluminum, TPU, and acrylic foam damps vibrations to promote a softer, more responsive feel. These irons are forged E9 Pwrshell Face Technology that offers a thicker face design that'll expand the sweet zone for a higher launch and faster ball speeds across a larger area on the face.