Which Penetrox ti use ? September 5th, 2007 Contesting’s walking encyclopedia, Frank W3LPL, answers the question of why there are two kinds of Penetrox. “Penetrox-A uses a Vaseline suspension. Vaseline can be problematic with rubber and some other materials. Penetrox-A13 and -E use a synthetic suspension. Types -A and -A13 use aluminum particles, while -E uses copper particles.” http://pdf.directindustry.com/pdf/fci/fci-burndy-electrical-master-catalog-edition-2007/12371-14523-_579.html