Here's an aftermarket accessory for Kahr pistols that you don't see very often.

[gb6491]

http://i64.tinypic.com/2u6h6ar.jpg
From what I've read, it's a hollow guide rod filled with mercury and a steel ball (or multiple balls).
They were also made for other firearms, but I believe they've been out of production for a while now. I've read that some folks like them, while others say they don't do anything. The photo is of one currently on gunbroker (605743065).
Regards,
Greg

[Scarywoody]

I remember seeing those years ago. I'm no physics guy but I'm sure there was some value but probably not enough to justify the product.

[deadeye]

To me it looks like an answer looking for a question. Can't say as I've not tried it. (Or really needed to.)

[dustnchips]

I think the answer is that the manufacture came up with something to make money on.

[Phish]

I had one my 1911 when I shot bullseye long time ahgo. It actually worked very well but not when you shoot very fast emptying the magazine tho.

[Bobshouse]

Similar to a mercury recoil reducer. They are fun, but don't really work that well (least in my shotgun).