Narrow, Fine

These pulses indicate a dearth of mediumship and Qi.  Depending on the position, there is insufficient Jin-Thin Fluids, Blood, Ye-Thick Fluids, or Jing.  The Thin pulse indicates a deficiency of mediumship whereas the Narrow pulse indicates that both mediumship and Qi are deficient.  

Feels like: At the extreme end of the Narrow spectrum, the pulse feels like a fine thread under the finger.