Hi, I was wondering why some strings such as bg-80, bg-66 say they have more repulsion then strings like bg-65, is it because of their thickness or some special core? I mean lots of people seem to prefer strings with more repulsion, but could the repulsion part be all in the head, from the advertisements? I personally don't find much difference in strings except for tensions. But that could be me.... so does a more repulsive string really give "more repulsion"? Thanks!