What part is this?

[Sarah36]

Which hose is the thin one with Norma flex written on it. 
My car gave up because it had become brittle and chucked out all the coolant.

if anyone can name it specifically and knows where to get one that would be great. I’ve tried all over the place. 

[AndyR]

Hi there, can you see where it is supposed to be connected to,  and is it coming from the radiator, or the thermostat?

[Vauxhall Owners Club]

think it may be the expansion bottle overflow hose which allows coolant to expel into the bottle