A smooth, tapered one piece sound tube of internal stepped bore construction based on Killion acoustic horn principles. These are used to increase high-frequency response. They can be used alone or dampened.  

3mm - Will increase the high frequency response by 8-10 dB in the 2000 to 5000 Hz range.
          This size is great for children and small adult sized canals.
4mm - Will allow an increase of 10-12 dB.

Horns sold separately.