Gruvgear FretWedge SM 2 Pack Black

Great look and fit, but they don't fully dampen the bass strings on inverted headstocks. It's sufficient, but you might want to combine it with the fretwrap when recording. Works fine on my '80s strat, but they may not fit properly on all straight headstocks depending on the tuner shafts' and string guides' height. They're probably sufficient for 3+3 and angled 6-in-line headstocks, but I'm sceptical when it comes to bass guitars.

It may not the end-all-be-all for muting all headstock's string resonance, but it looks much better than foam.