Turn the ultem part that’s inside, the bit the tip goes into. It must be able to move, the whole thing is just held together with o rings. It might just be a bit stiff. You could try taking the bits apart to get an idea how it works.

 

For me he nextera is much better than the dvarw. Speaking of which I need to empty my dvarw and put it away...

 

It wouldnt move at all by hand so gently tried with the pliers and its worked. Thanks I need to be a bit more unforgiving with new tanks - I'm always worried about breaking them.
Cheers both, Ive got a nice little mtl range to choose from now.

 

Enjoy!