CP4 pump model question


Registered User
Can anyone tell me what the H stands for in the model numbers on the pump.
Eg. CR/CP4HS2/R90/40-S
I am upgrading the pump in my audi a5 3.0tdi
It seems that all the higher output engines seem to run a pump that has a H after the CP4.
I know that R stands for right hand turning and that the bigger the number after the R means it should flow more fuel.
I have found 2 pump that should be a direct bolt in.
and also a

Iv tried searching but with no luck.
Can anyone help me please