Plastic buds

[RetroJulia]

You know those plastic cylinder thingies that retract / shrink when you heat them up ? I need to make some kind of a seal to something I don't want exposed.
But I have no idea how are they called. Anyone knows how are they called ?

[HisMastersVoice]

Heat shrink tubing?

[Jerry B.]

As a Journeyman with the power company, we would purchase a shrink sleeve to give some insulation value for our low voltage tools such as a screwdriver. We would slip it over the shaft and shrink it with a torch or heat gun. Is that what you desire? Jerry Blais

[RetroJulia]

Heat shrink sleeve, that's what it was called. Thanks a lot guys !