The hose's job is to carry brake fluid from the master cylinder to the caliper on the wheel.
Its flexibility is what allows the wheel to move with the suspension.

Each HEL Performance brake line kit is assembled at their Devon based works from the finest quality stainless steel fittings swaged directly to hard drawn tensile stainless steel braided hose.HEL brake line kits eliminate that spongy feeling often found with rubber hoses under extreme braking conditions - the time when performance is needed the most. By replacing the original hoses with their brake line kits you will remove this sponginess and your braking will deliver new levels of precision.