Air line sizes

It is very complicated! If you break up an inch up into sixteenths there are sixteen of them in an inch. So a number 8 is a 1/2 inch.
Replace as it came from the factory as far as sizes go.

 

Hose is sized by the inside diameter too FYI.

 

I just recently learned they are not color coded to sizes. I always assumed they were. Needed 1/4 inch and took a piece in that was green. They gave me a roll of black and I questioned it. Even one of the employees didn’t know it.

 

Bought some yesterday at Freightliner in Ocala Fl. It cost $7-$8 per foot. It’s called Stratoflex. Black steel braided hose. Same as factory. The # 10 is marked 10mm and 1/2”. The # 6 is marked 6 mm and 5/16”. I’m using it for fuel lines. My steer brake lines are # 8. My drives also look to be # 8. Except for the 2 chambers with parking brakes they look like #10. No idea what’s in between tanks and valves. I don’t know what the # 8 mm is supposed to be or is marked as in inches. Maybe 7/16”? I also don’t know how they come up with those #’s, because they aren’t correct conversion #’s. But I just double checked my new #6 and # 10. Haven’t put them on yet. Got them up in the cab. That’s what’s marked on them.

 

Get some of these to use with bulk hose.

 

I just realized you were referring to brake hoses and I was talking about the plastic air lines. Sorry for any confusion I may have caused.

 

Stratoflex was an independent company that fell into the Parker empire. Ends on that type of hose are reusable.
#10 hose is 5/8's, no MM match there. 10 MM is in between 3/8's and 7/16's. 1/2 inch is #8 and about 13 MM but there is no 13 MM hose. #6 is 3/8's , 6MM is closer to a 1/4" but no match there as well. 5/16 is about the same a 8 MM.
My reply is very confusing but I just tried to answer each thing in the order of your post. Some of those numbers you listed may have been part and or series numbers on the hose.
Then when you get to thank you are pretty smart, that was me. A man came in and wanted four hoses to go through a big forklift mast. They were 3/4 " and had 12 stamped on the ends. I made them 4 hoses with #12 female JIC ends and set them on their way. About 2 hours later they came back made as hell. After they feed all that through the mast the ends would not screw on. I called my supplier. Oh those are Japanese #12's. What the hell is that as it should be smaller than a 1/2 inch?
The outside hose diameter is not what you are looking for as Amodel said. Looks can be deceiving.

 

The stuff I bought is clearly stamped #10 and 1/2” . The other size is stamped #6 and 5/16 is harder to see.

 

Not much surprises me any more. I bought this with a new radiator about a year ago. Yes it is a lye as it is still rightie tightie and leftie looseie.