Drive shaft ,pls Help

[Question]

Hi, I have a Traxxas rustler 4x4 and bought the tekno big bone drive shaft. On the page where i bought it it says only 1 o ring in a cup is that right ? Because on other sites like yours it says 2 o rings in one cup. But I only had 2 o rings in total.
Here is the link
https://www.modellbau-metz.com/modellbau/tekno-rc-tkr6765---big-bone-center-driveshaft-and-outdrives
Thank you very much

 

[nub]

The company that manufactures the kit says:

* The O-rings go inside the drive cups two in each cup.

 

[Question]

OK, I wonder why only 2 o rings were included :/
Should I just buy 4"2mm after Air Amazon?