I just thought I'd mention a good material for representing ropes and small cables.
I used to shoot competition archery, and for tieing equipment and sandbags onto 1/35th armour, serving thread is great stuff.
It is used for wrapping tightly around bowstrings in areas of high wear, like where the arrow clips onto the string, or where it wraps around the cams of a compound bow.
The good stuff is made of a nylon and kevlar type material wound together, and is gunmettal in colour, so it looks like a fine cable. It does not fray easily and the ends are easily melted together with a match so it doesn't unwrap on the ends like some string does.
The downside is it isn't cheap, but a roll that costs $30Au will fullfill you needs for a long while.
There is also a monofillament version which is just like black fishing line, and does a good job looking like a hydraulic line for things like Academy's M113 Fitter .

Anyway, just thought it may be of interest........

Does it come in different mean diameters, or just the one size?

There are different manufacturers, so the thickness does vary, and some grades are made in slightly different sizes. The straight nylon stuff is the thickest and when painted looks like rope, and the dearer stuff (labeled "Fastflight" or "Spectra") is thinner, is a nice gunmetal colour, and looks like steel cable. The Fastflight doesn't take some paints well, but a rust wash works on it.
The rolls that cost about $30 here in Oz hold about 100 yards so they will last for a while.

I was prompted to mention it because while I was checking out a few modeling sites yesterday, I found a pic of a very nicely done Sherman that was spoiled by having it's stores tied down with what looked like very fine twine. The thread had more whiskers than I do, and detracted from a very nice model. Fastflight doesn't fray on the sides and the ends are easily melted together so it doesn't undo there either.

I have an Academy 1/32nd Neuport 17 in my "I'll build that soon" pile, and it should be just right for rigging it as well.......