Name of tap part

[confused2]

Hi,
I'm trying to fix my taps.
I know which part needs replacing, but I don't know the name of it, I would appreciate it if someone could tell me the name of the part.
Also where would I be able to purchase this part?

I have enclosed photos below, the part in question is circled in yellow:





Thanks in advance.

 

[Vic Spanner]

What area of UK r u in.

 

[Bahco]

Just as well to replace the whole cartridge for a fiver or so.

I haven't got a clue either as to what its called.

Probably don't sell them separate anyway

 

[PlanetThanet]

Hi

Armitage Shanks .

Spline adaptor.? Call then and ask, I think they would send you some FOC.

Thanet.