Originally Posted by DMF
A curved hard tube?
On linear pull brakes (usually found on mountain bikes), cable housing typically leaves the last cable stop on the top tube and is inserted into the end of this metal tube (noodle), which curves back to the brake. The noodle has a plastic liner inside it that the cable runs through (this is what the OP was asking about). On the front brake the setup is similar, but of course there's no cable stop involved, the cable housing just curves down from the brake lever and is inserted into the noodle before it gets to the brake. Front brake noodles are a little longer and a little less sharply curved than rear brake noodles-