Building up my new bike with a Jagwire Road Pro Complete Kit and the brake cables are double-ended, very nearly identical with one slightly smaller diameter marked "CC" and the other more rounded on top marked "CS".
After a bit of research, discovered that the smaller, flatter, CC end is for Campagnolo, and can be cut off if you're installing for Shimano/SRAM as I am
Likewise, the shifter cable end fittings are double ended, the slightly larger ends are stamped "JC" and are for Shimano/SRAM, and the slightly smaller ends are stamped "C" and appear to be for Campagnolo.
Here's some measurements I found, which match up pretty closely with my Jagwire kit:
Brake cable end fittings:
Shimano/SRAM "mushroom cap" diameter: 0.238" (6.05 mm)
Shimano/SRAM "shank" diameter: 0.140" (3.56 mm)
Campagnolo "mushroom cap" diameter: 0.214" (5.44 mm)
Campagnolo "shank" diameter: 0.138" (3.51 mm)
Shifter cable end fittings:
Shimano/SRAM end barrel diameter: 0.173" (4.39 mm)
Campagnolo end barrel diameter: 0.159" (4.04 mm)
Just thought that might be useful info for someone else in the future!