On a recent trip to Bonaire, N.A. my wife and I dived with a couple from England. They had a signaling device that was about the length and diameter of a pencil. It was hollow and was made out of some type of metal. It had small metal pieces inside the sealed tube. The small unit was then attached to the BC. With only a quick shake of this tube, there was a "very" audible sound that everyone easily heard. This device produced the most attention getting sound of anything, non-air integrated, that I ever heard. The problem is I am trying to find one in the US and nobody I talked to ever heard of it. I'm guessing it is a European product that may not be available in the US. Any help with locating one or at least the manufacturer name would be greatly appreciated. The ease and sound of this device put our tank bangers to shame.