Clay at EMF Rod ends or Team Tube. for rectangular tube I buy from reliable tube. ERW is roughly $1.50/ft cheaper, but DOM has more yield strength. I personally would use ERW for things such as fenders, tire carriers, non structural stuff if you want to save a bit $$ and DOM for links, Cages, structural stuff. But the best stuff for Cages is R-8 Docol when it comes to safety in racing applications. I'm picking up 100ft of ERW and 96ft of DOM when im home Sept 8th.