Sunlite SIS Housing Boxes

SIS stands for Shimano Index System. This designation indicates that the housing is specifically designed for indexed shifting, meaning it is compressionless to ensure the cable doesn't stretch or compress under tension, which is essential for precise gear changes.

No. This is specifically derailleur housing. Brake housing is constructed differently to handle the high compression forces of braking, whereas this SIS housing is built for the specific tension requirements of shifting systems.

The 30mm length refers to the size of the individual housing ferrules or end caps contained within the box. These are small, critical components that sit at the ends of your cable housing to prevent the housing from fraying and to ensure a secure fit into your frame stops or derailleur.

While it is designed for indexed systems, it will work perfectly fine for friction shifting as well. The compressionless construction actually provides a very smooth, consistent feel for friction shifters, though it is technically over-engineered for that purpose.

You should consider replacing your housing if you notice your shifting becoming sluggish, ghost shifting, or if the outer casing is cracked, kinked, or showing signs of rust. If you are replacing your inner cables, it is almost always best practice to replace the housing at the same time to ensure optimal performance.