okay I am trying to build a frame where some parts stow inside other parts...

it looks like NRS uses 1.625 OD/1.375 ID aluminum tube even though they say that its pipe (yes there is a difference).

now looking online I see I can buy 1.375 OD tube as well - so will this fit inside the 1.375 ID tube?

also most fittings like holleander and keelite are for pipe sizes not tube sizes - which is probably why NRS makes their own - any good source for tube fittings?

many thanks.