Can anyone tell me the name of the threaded fitment I have connecting
a 15 mm flexible pipe with a female 1/2 inch BSP end to the female 3/4
inch BSP fittings on a bar thermostatic shower?

Unfortunately my card reader has packed up so I am unable to post a
picture.

It is a fully threaded 2.5 inch long fitting, with a male 1/2" BSP
thread at one end (to connect with the flexible pipe), and a male 3/4"
BSP thread at the other end (to connect with the shower fitting). I
have also noticed that the fitting has a mesh filter so would seem to
be a dedicated shower fitting. I need to know what they are called so
I can get hold of a pair 1/2 inch longer (i.e. 3 inches) as I have
strengthened the piece of plasterboard they go through with a thicker
piece of wood.

I posted about this before, but did not make myself very clear, for
which I apologise.
Keith