10 and 11 speed gear changing needs good quality cables to get a precise, smooth gear change. Many cable manufacturers offer PTFE coated cables for this purpose. PTFE is a coating similar to that on a non-stick pan so you can see why it is helpful in getting that precise gear change we're after.
These cables are great as long as you change them regularly otherwise the cable will start to shed its PTFE coating as shown in the photo above. Once the coating starts to come off it actually causes friction as it gums up the inside of the cable casing. I do fit PTFE cables but many of us don't always get our bikes serviced as regularly as we should so I will use polished stainless steel with a good quality outer casing as a good alternative.
If you need help remembering when you last had your cables changed then The Cycle Mechanic provides all clients with a full service history simply by logging in to this website. "The Workshop" client area also shows a copy of the sales receipt and credit card receipt for each transaction.