Shure Sound Isolating SE425-CL Manuel D'utilisation page 7

Changing Sleeves
Caution: If the barb or any of the nozzle is exposed, the sleeve is not properly installed.
Replace sleeves if they do not tightly grip the nozzle.
To ensure proper fit and performance, use only sleeves supplied by Shure (unless us-
ing custom molded sleeves).
Twist and pull to remove the sleeve from the nozzle.
Slide on a new sleeve so that it completely covers
the barb and the nozzle.