I often see people using these:
They're great if you want to:
Keep the air in your clarinet bore from circulating by trapping excess moisture.
Keep your bore as humid as a tropical rain forest and develop a nice patina of mold in your bore and on your pads.
Encourage your skin pads to rot.
Develop leaks when the "fuzz" comes off and sticks in your tone holes.
Suddenly be unable to play because the fuzz accumulated in your register tube.
Or you could 💩-can 'em and swab the bore out with a good swab every time you finish playing.
Stacatto Samurai out.