Hrc expansion bottles

What's the need for these? Do the race bikes not run a coolant resevoir?

 

A lot of people with race bikes do away with the bottle located down near the swingarm pivot and instead use the small 'HRC' bottle mounted typicaĺly in the nose for the radiator overflow.
Another bottle is used for the fuel tank vent.

 

So is the cooling system filled via the cap near the rad then?

 

Yes, that's right.

Here is a pic of my set-up

 

I got some bottles spare I think still