Grommets

[Richard J]

I have a Weber wood nymph, https://themandolinstore.com/product...er-wood-nymph/

[j. condino]

".....Sometimes on stage I sweat like a whore in church writing a bad check with a stolen pen....."

[David L]

I do believe I'd definitely have sympathetic vibrations without them because if I don't mute them, my bass stings will hum if I'm playing the high courses.

The bass strings humming when you play the high courses has nothing to do with the grommets. The bass strings sympathetically vibrate when you play higher notes that are overtones of the bass strings. This can be solved by lightly touching the bass strings with the heel of your picking hand. Electric guitars are notorious for this because of the volume and vibrations from the amp. I have to do this on my banjolin to get rid of extra reverberations. Muting the strings behind the bridge does nothing for this.