like completely felt or like a plastic pick covered with felt

i dont think it could damage your strings either way
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why are metal musicians prone to fatness?
Cause there music is heavy.

Writing music is hard D:
Those are generally used for basses
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I can't see them damaging anything, but I can definately see you ending up with a bunch of tiny hairs coming off your strings after a while.
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well, if they ruin your guitar, then they wont make em. So, there not gonna ruin em , just some threads, and besides the fact that is feels like your playing with a piece of carpet........