I’m currently finalising some grip kit I’ve been designing and numerous parts must mate with speedrail/scaffolding. There is 1 ¼” and here in the UK its 48.3mm for the scaffolding. I know in the US 1 ¼” speedrail is pretty prevalent but I presume a larger tubing is also used. The 48.3mm scaffolding is often referred to as an EU standard so am asking if the larger tubing commonly used on US sets is also 48.3mm or another size and if so what it the standard over there?

Any help much appreciated.

1 1/4" and 1 1/2" are common here.

Thanks Edward, from what I now understand that's internal diameter your referring too. I think that makes the 1 1/2" 48.26mm OD and the 1 1/4 42.16mm OD.