Z bar threshold but which size?

[grifter]

If any carpet fitters see this, can you answer this please.
Having carpet fitted on the landing and there are 4 doors which need z bars.
The fitter showed us these matt black ones which are the special prem dble Z 9 90.
Due to the price, we are sourcing our own ones but the floor level into a couple of the rooms, being tiles are between 25 - 30mm from floorboards on the landing to the top of the finished floors.
We were told to get these size bars, but will they fit to accommodate the height? Unless I'm missing something? Do they adjust in height when fitted to account for varying heights. The underlay is 9mm and the carpet is a fairly thick pile.
I don't want to order the wrong ones

 

[crazydaze]

The fitter will either raise the bars on strips of ply or may use Stairrods UK Easy Shims (the same supplier of the Premier Double 9 Bars.

You wont find a better bar than a Premier Double 9, especially in Black, the cheap Black bars mark and scratch very easily, the black finish on the Stairrods bars is much harder wearing.