Etymotic ER-4 microPro Manuel De L'utilisateur page 6

CLEANING AND REPLACING EARTIPS
Over time eartips may lose their elasticity. For best performance and
retention, replace 3-flange eartips every 60-90 days. Replace foam
and glider eartips frequently.
To clean 3-flange eartips:
1. Remove the eartip from the earphone.
2. Clean with water and mild soap.
3. Dry the eartip before placing it back on the earphone.
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