Which Braking System?

[Bigdave]

So I'm in a pickle.. 

My 2012 A4 needs brake pads and I know which ones I am going to buy, however,

Trying to order from Euro Car Parts and theyre telling me I have to choose wether I have the Lucas or the Teves braking system.

Sadly my calipers seem to have been replaced at some stages and all are TRW branded, so I've no ideas how to tell it all apart thought stripping the thing down.

Anyone got any tips on how to tell the systems apart visually etc?

[Audi Owners Club.]

There should be a diagram or dimensions for both sets of pads somewhere on the internet....best to identify them first but if not, buy both and return the ones you don't use