[Bob Parmenter]

Hey Tim,

Aluminum is alloyed for various purposes, so thickness isn't the criterion. My applications have all been the standard 3" collector end. The "gaskets" I refer to are available from Summit. There may be some guys on the site here who are into metalurgy and would know better how to explain it, or know the i.d. number for this particular alloy, but you might try a metal supply house in your area and see if the term "dead soft" is some form of standard terminology, or industry slang. From observation it is a soft alloy of aluminum that is easily compressed (relative terms) which must be what contributes to the sealing. One thing I have noticed is that it will make a "clicking" sound as it thermal cycles that I didn't notice before I installed them. I don't find it annoying, but others might.