Function: Prevent the steel cores in the brake pipe from breaking the stop bolts under the strong tension during braking, affecting the normal braking function Advantages: Smooth edges, will not hurt the cable housing Material: Black color, made of quality plastic material. Lightweight, strong pressure resistance and durable Size: 4mm length: 18mm, suitable for variable speed lines tube with a diameter of 4mm; 5mm length: 17mm,suitable for brake lines with a diameter of 5mm Package: Includes 100Pcs brake cable wire tip cap, 100pcs for 4mm derailleur/ 100pcs for 5mm brake cable, optional