The cables often are also called shift cables, the English term which is also used in German. Every once in a while you'll find people still calling them Bowden cables since a Mr. Bowden has once invented the cables on the bike. They are available made of steel or, if you make the better choice, namely made of stainless steel. Shift cables have a diameter of 1.2 mm or 1.1 mm, which is identical for MTB as well as for road bikes. On the cable end, there are cylindrical cable pods. The inner cables require so-called end caps and the exterior housings also require end sleeves, which sometimes can be coloured, too, and thusly grant the cable ends a little colour and emphasize eye-catching accents if you desire a certain colour system on the MTB.
The main brands are Jagwire and Shimano if you need MTB cables. Instead of separately putting together the inner cable, outer housing and small parts, you can also fall back onto a complete gear cable set, meaning everything is included and compatible in one package/set.
We recommend to choose high-quality cables of stainless steel and PTFE coated. The Teflon coating results in fluid switching operations since the loss caused by friction is minimised. You'll also find the necessary small parts in the selection, such as for example cable adjusters. These are small helpers which readjust the cable by turning them and that is how you can fine tune them.