This unusual mute slides onto the strings between the bridge and tailpiece. It's made of nickel-plated spring steel, with clear flexible tubing and brass spacers. The mute slides on a pair of strings to adjust the nature of the sound, and can even be (according to the manufacturer) effective in dampening wolf tones. It can be pushed closer to the tailpiece, remaining on your instrument, when not in use - and be slid up towards the bridge and on top of it for various tonal effects.
They have become popular with some players, particularly bluegrass, who feel it helps achieve their goal of more thump. This device is marketed as a mute but has a different effect than our other bridge mutes, which limit bridge vibrations.
In by humble opinion, calling it a mute may be a bit of a misnomer. I guess what I'm saying is that the effects are very subtle, so don't expect a huge difference in your sound. Trying it out on my Juzek bass with Corelli strings, I can detect some changes in the overtones, as well as some slight suppression of sustain, but it depends on location.
Yes, the mute does look a bit like one of those wire puzzles you buy in the magic store, but it actually mounts quite easily. Check out our very short video showing how to put it on your bass.