Anyone got one rolling around in a drawer somewhere that they're willing to part with?

Would like to buy one for my J-Bass -- just to see what it will do.

Call me cheap, but I just don't feel like paying $32 for a new one if I don't have to.

Try putting a C-clamp on the headstock. That will give you the general idea of what the product will do.

Basically.

Is this one of those things that adds mass to the headstock? Jeremy is actually quite right that you should experiment with adding mass first with conventional objects around the house (because mass is basically mass after all as long as it is distributed roughly the same). If you can get something that weighs nearly the same then you probably have a good approximation.

What adding mass will often do is it will make the bass neck flex a lot more--this is energy that does not get converted into sound but rather into microscopic motion in the wood. You can prove to yourself that adding mass will increase the vibrational amplitude by tying a plastic ruler down to the edge of a table and flicking it... then add two pennies taped on. The wavelength and amplitude will both increase.

This in fact tends to lower the resonant frequency and can cause more dead spots rather than fixing them. On the other hand, replacing heavy keywinds with lighter ones tends to do the opposite and I think it is a much more logical solution to the "my bass has a dead spot" problem. If you have a Jazz Bass it should be VERY easy to find lightweight tuners that will directly replace whatever is currently on there, and it is my passionate opinion that this will get you much further than adding extra mass. It is also my opinion that adding mass is usually not a good idea at all.

Apparently this varies from bass to bass. Joshua & others have improved sustain on some basses by taking mass away from the headstock. However, earlier this week I tried to see if I could fix a dead spot by removing 2 of the 4 tuners from one of my basses, and it made no difference. However, adding the Fat Finger to the end of the headstock did the trick.

So some basses need less mass, and some basses need more (and who knows, maybe some basses could go either way; it takes all types to make a world). I recommend experimenting with your bass to find out which way to go before buying anything.