Shimano Optislick Inner Derailleur Cable (Shimano/SRAM) (Stainless) (1.2mm) (2100mm) (1 Pack)

The secret is polymer coating that when viewed under a microscope looks like a series of tubes wrapped around the cable. This means less surface area rubbing the internal housing liner and it holds grease longer. Main benefits are significantly less shifting effort and the feeling of a quicker shift action.