Etymotic The BEAN® Quiet Sound Amplifier® - Manual (Page 8)

SELECTING AN EARTIP
English
ACCU•Fit ™ Eartips
7
Selecting an eartip:
No two ears are exactly alike. The eartip that is most comfortable
is the best choice, but it must seal well to prevent feedback (whistling).
When changing eartips make sure the eartip fits securely
on the stem of the device.
incorrect correct