für with genitive?

From Module 13.3 Business Call

"Es geht um eine große Werbekampagne für eines meiner Produkte"

with preposition “für,” isn't it always supposed to be followed by the accusative? “Eines” is genitive. 

What am I missing?

Thanks.

I see. “Ein” in this case is not an article, but a noun substituting for the word “das Produkt.”   I'm not sure where to look for the rule governing this, but when used as a noun, “ein” will have to also carry an appropriate ending.  

As in the accusative:

Ich sehe einen der besten Studenten. (der Student)
Ich sehe eine der besten Läuferinen der Welt. (die Läuferin)
Ich sehe eines der besten Fahrräder. (das Fahrrad)

Just when I thought I was starting to get all this! 

Yes, ein(e)s is an indefinite pronoun in the accusative, it is only meiner Priodukte that is genitive.

It's pretty confusing as the indefinite article eines is masculine or neuter genitive.

This one got me too. :)

You should find this in your Mcgraw Hill grammar book

Indefinite pronoun! 
 

Yes, that's what I was looking for, and that's what it is. 
 

It turns up now in grammar searches, a little elusive, but it's definitely out there. 

Hallo gottahaveajava und sfpugh,

It's great to see learners helping each other out in the forum! It's a little confusing, but you're right in saying that “für” is always followed by the accusative, hence the indefinite pronoun “eines” is in that case. 

You can check this by asking “For whom or what is the marketing compaign?” and the answer is “für eines (meiner Produkte)”, thus, it is in the accusative case. 

The genitive case is used to show possession. You could ask “Whose products are they?” - “They are my products.” “Meiner” is a possessive pronoun. Often the genitive is replaced by “von” (from) and the dative, so you could change the sentence to:

"Es geht um eine große Werbekampagne für eines von meinen Produkten."

Hope this helps!

Julia