What's the rubber tube in my puncture repair kit for? I've got an old school puncture repair kit, the type with glue and patches.

As well as the sandpaper, patches, 'vulcanizing fluid' and instructions, there is a 2.5cm long, 3mm wide, beige rubber tube.

What's it for? 

(it doesn't seem to appear in the pictorial instructions)
It is the Dunlop valve, it was used a lot in Holland, UK, etc. 
You can see it in action here:




But currently it is replace by the Blitz: