[Vocabulary] CONTENT / CONTENTS?

[Jack8rkin]

Hello!
I got a question related to the use of the word "content/cotents". I heard there is a diference between AmE and BrE, but I still need to understand it more clearly.

There are phrases like:
boron content in steel
fission product content in fuel elements

What a form should I use here (Sg or Pl)? Content or contents?

 

[tedtmc]

boron content in steel
fission product content in fuel elements

or lead content in petrol
or carbon content in steel

Content here means the proportion of the item in the compound/mixture, usually expressed as a percentage and is singular.

not teacher