C-type (horseshoe) iu tuning ordinary cotton earplugs, earplugs unit for about 15.4MM use.
Can be used flexibly depending on the shape of the trimming unit of pores.
Also be used to seal the sound of the earphone housing back hole.
Tuning up cotton may increase the role of sense of low volume unit, changing the sound quality.
Some headphone tone changes over time, it may be because tuning cotton aging,
Such as the replacement of cotton may play a role in tuning to improve the tone of the other old Cypriot re-hwan youth.