Shure SE420 - Manual (Page 6)

CLEANING THE EARPHONE NOZZLE
If you notice a change in sound quality, remove the sleeve and check
the nozzle of your earphone. If nozzle is blocked, clear obstruction
by using wire loop end of cleaning tool.
Nozzle
Wax Removal Loop
When cleaning, do not force any object through the earphone
nozzle! This will damage the earphone sound filter.
Cleaning Tool
Nozzle Barb