These are metric brass tubes all with a wall thickness of 0.45mm which means they fit inside each other with a very nice fit.
So 2mm will fit in 3mm and so on.....

All sizes quoted are the OUTSIDE diameter.

These 300mm or 100mm long the sizes in the drop down box are outside diameters 

INTERNATIONAL BUYER PLEASE READ BELOW

Royal Mail Airmail (small packet) is NOT a tracked or insured service.

Royal Mail International signed-for is tracked and insured upto £50 these are royal mail prices not mine and is completely of of my control.