[Fire and Ice]

I am currently building 2 Cat K1 Aero's and need a little noob advice.

The plastic yokes that came with the car fit straight on.

The 7.5 Alloy yokes come with a load of washers, Sorry for the daft question, but What do I need them for and where do the fit, ie 2 in front 0 in back or 1 and 1, sorry but having a blonde moment and just want the cars to be great for when they hit the track without parts on backwards or sorts.

Thanks for any help and advice given.