do you have your measurement certificate? it is on that, if you don't you can email ahpc and they can mail you a copy. it will be in millimetres that is a tad more accurate than to the inch...
Andy, you're going to have a hard time finding a 40 x 1.6mm wall in the US. I actually don't know anywhere you can. I personally think a slightly thicker wall is worth it all day long and most of what you find in the US will be. The stock plug won't fit in these but Jill has ones that will. -Todd