Paul, I've noticed that some of your questions are about things that have been discussed many, many times.
You might want to try using the Search button. Go ahead, try it now with 'round tube'.
If you need more information, you can post a reply to one of the old threads to make it active again.
And there you have it
http://www.locostbuilders.co.uk/viewthread.php?tid=7521
thats a good one....