Power Steering Box O-ring size

[Caesium]

Hi all,

I'm trying to fix a leak on the side of my steering box. Its the (valve?) cover with the 1 on it, on the side where it bolts to the car.
I tried a 24x3.0mm o-ring from NAPA but on install it seemed to shave some of it off... Dealer will take to long. I was wondering if any one knew what size it is? part number is 009 997 44 45... Could it have just been installer error?

Nathan.

[Caesium]

So I ordered some from the dealer... It will take a few days. I would still love to know the size...