I am thinking about going with a round air bag flat bottom steering wheel for my A4. Are they all compatible? Anything I should know?

Looking at S3 wheels like this:

http://www.ebay.com/itm/Audi-A3-Q3-S...lZvdQw&vxp=mtr

And an airbag:

http://www.ebay.com/itm/Audi-A3-Q3-S...lZvdQw&vxp=mtr

Any advice would be appreciated. I'll also consider anything you might have for sale.