CLB had brake cable kits which used aluminum coil in the housings. Yes, very light!

I fitted such housings on Joe Englert's carbon Willier build, got the weight down to a very low 11 POUNDS figure or 5kg.

He's on road-worthy 24/25mm clinchers (albeit with no bar tape), full-carbon saddle (I've ridden the bike and it's fine).
He's well on his way to climbing 1 million feet in 2021 after riding the same bike 20210 miles in 2020.

Same housings as I fitted to this old 22lb French bike. Colors offered were clear (shown), smoke, red, blue and yellow.




EDIT: I should have mentioned tat the CLB housing is lined. It's a bit squishy and is more vulnerable to kinks or deformations but is very smooth. Squishiness tends to be more of a problem as the weight load increases, why fly-weight racers usually feel less "need" for disc brakes even in hard conditions.