Shimano sl bs79 outer cable guideshimano recommends the use of these sl bs79 outer cable guides when you are running outer cables under bar tape ie higher end sti levers or bar end shiftersbrakes they hold the outer cable straight and prevent the bar tape causing any kinks or narrowing of the outer which could affect shiftingbraking performance it is also useful for bars without cable grooves as they help to retain the free cable movement but are also comfortable when under the bar tape