Jagwire Pro and Elite kits are readily available... they feature lined housings and smooth ground stainless cables.. the elite cables are teflon coated for even smoother action.... two of my personal bikes are set up with Jagwire Pro kits, and the Trek 930 is set up with an Elite kit...

Shimano sells some kits also, but not as easy to obtain... their SIS Shift cable housing is a STRANDED type that eliminates compression of the housing, which dramatically improves indexed shifting.... not sure what their brake housing is called, but it works well too...

cheaper housings use a SPIRALED WIRE in the housings that is, well... a SPRING of sorts... Yes, they compress when you clamp down on the levers when braking for that hair pin turnn at the bottom of your favorite descent! better brands of standard housing are Clarke's and Aican

i stock Shimano and Clarke's housing in my shop... i avoid the super low budget junk. I order Jagwire kits when the customer requests higher performance from their bike.

oh, and the jagwire kits come in a rainbow of color choices... there are lower cost Jagwire "kits" on EBay... they may or may not be "Jagwire", and quality is inconsistent! the elite or pro kits IN THE FACTORY PACKAGE are a good choice... kits include end caps and other fun goodies to complete the setup.