supplied framing metal

I was wondering if anyone had details about the 2"x4"x36" pieces of extruded aluminum that we recieved in the kit. I was told by someone to ask what type of aluminum it was. I don’t know much about it but apparently it makes a difference when welding. Any input would be helpfull.

I’m not totally sure about this, but I can say this most popular alloy is 6061.

hmmm, anyone check out the parts list yet?