What Joe said above. 22 gage and 16 gage. The final number is the color that corresponds to the Resistor Color Code. For example M22759/11-22-0 is a Teflon (PTFE) Insulated, Silver-plated copper wire with 19 strands, rated at 600 Volts and 200 Deg C, in Black.
You can find it on ebay if you search that Mil-Spec number. Only buy from legitimate sites in the USA. Lots of wire on ebay is from China and not Mil-Spec, no matter what they say. Often plastic insulation that melts when you turn on your soldering pencil.