Yesterday there was a question on the Starduster board about what aluminum to use to build engine baffles and he wanted to know where there was an explanation of the metals.I started to reference the Aircraft Spruce Catalog and it wasn't there. So I dug in the trash for my old catalog. The descriptions are in the 2009-2010 catalog and not in the new 2011-2012 catalog. So just in-case some one hasn't noticed you might want to save that catalog.