I never tried the air route, I was always afraid that they'd fail, but I guess the good ones don't - I don't tow that much anymore, so I just drive with steel :-)

I know that when the air stuff first came out, they would be prone to leaks, etc... so I guess now they are rock solid? I think the older units would get moisture in there, and rust, etc or corrode, etc...

hey Aqua - does your son still drive his truck with the steel seal working? - just curious.