1972 commando breather pipe diameter

Could anybody tell me the breather pipe diameter for a 1972 commando?
Part n. 062619
Thanks

I know I know, nominally .8", actually .74" so same size Herring bone hose as oil hoses, so ~3/8" fuel hose from auto parts standard or Moss Motors or a few other vendors for textured.

Yes, I also measure 3/4" ID hose.

Ok thanks,
3/4 ID
ID means internal diameter?
So in metrical is 19.05 mm, is it correct?

The breather hose outside diameter O.D. is 3/4", the inside diameter I.D., which is how hoses are termed, [regardless of how thick the rubber], is ~3/8" and what you'd ask for in America for something that'd work on the Combat breather hose fittings.

Ok understand
Thanks hobot

Ok, we need to know what end you are speaking of. If it is the oil tank end, then it is 3/8" If it is the actual breather connection then the dimension of the breather itself is close to 15mm or .593".

There is also item 062617 that is an adapter to connect the 2 sizes.
1/2" from the breather and 3/8 to the tank connection.

I've the oil tank end pipe (3/8) and the adapter (from 3/8 to 1/2)
I need to replace the missing part , the pipe from adapter to the breather
Now I'm a bit confused
I thought i need a 3/8 ID - 3/4 OD but
If the dimension of the breather itself is close to 15mm or .593" would a 3/4 - 19mm pipe be correct?
and more...the adapter is 1/2 12.7mm the breather end 0.593 -15mm the ID of the pipe between them 3/4 -19mm?

Forget the 3/4". 1/2" will stretch over the breather.

Yep Pete reminds us the baffle fitting is 1/2" across and oil tank nipple only 3/8"-ish, so a hose size change section and adaptor elbow used in factory set up to connect to tank. The cheap plastic MotoMite brake valve has 90' bend with ~correct 2 nipple sizes built in so easy to replace the 90' elbow with this one way light action check valve up under tank by frame so only your mechanic knows for sure. Get 2 , if ya do, of these cheap $5-6 brake valves as they do get some engine heat and oil/gas vapors that decay them over a few years. You can try some clear tube for a while to see the wet sump clearing function of the Combat ingenious case vent location and some idea of how much yours does or does not over time. Try to keep ahead of re-torque or even best flapper valves may still leave a mess. Only a few places still have similar Herringbone textured hose for us, though used original seems to last forever.