Hello.....

Physically the difference is easy to identify via the weight. On the bridges I have the zinc weighs almost 3 times as much as an aluminium. Also when the bridge is said to be zinc that does not necessarily mean pure zinc. It could be made of 'scrap' all melted down together with zinc just being the largest contributing metal in the mix by volume i.e. 25% or 30%. Mass-production guitar factory engineers won't see the actual metal as being critical. The bridge has to be metal and support the strings....that's about it!!!. Low cost is far more important. As for sound, it's not so clear cut. The difference is not black and white at all. In fact I'd say that changing the nut from the factory plastic to bone or altering the capacitor values in the control cubby-hole would have more of a definable effect but even that can be relatively subtle. I used to chop and change all sorts of bits for years, and I wanted to believe that it always made a big difference. I became expert at convincing myself that I could hear a clear alteration in sound through my wise purchasing decisions. Complete crap! You would need an oscilloscope to record the differences in sound. In the end I do prefer Aluminium but only because I'm always trying to keep guitars' weight down. However, I must say that if these $150+ Aluminium stop-tails were the only option I would not buy at that price at all. I just buy Gotoh at approx $35-$40 nickel or gold. I don't know if there is a difference between the Gotoh stamped ones and the Gibson branded ones in terms of the purity and quality of the aluminium.