need to replace lower arms but on lookng got choice of 18mm or 21mm can i choose by reg plate or does it  need measuring? 

Probably safest to measure.

I thought it was age related, and that all facelifts would have 21mm but not totally sure.

I've also seen some sites stating that cars with xenons got 21mm which seems totally unrelated.  I thought it was because they were the same as ST/RS which come with xenons as standard but it seems the arms are different again on those.

I risked buying the 21mm BJ for my 08 1.6TDCi with xenons without measuring first but they were correct.

I had that issue and bought both and ended up being 21 (focus MK2.5 1.6) . 

there is a colour code to them.... blue and orange, i just cant remember which is which! if you check on the balljoint you will see (if you clean it up) a coloured ring.

if the colours match then your all good. I'm almost positive that its blue for 21mm... 

 

thanks guys think ill drop ball joint out in morning and measure it 

On 02/10/2017 at 2:50 PM, Dee_82 said:

there is a colour code to them.... blue and orange, i just cant remember which is which! if you check on the balljoint you will see (if you clean it up) a coloured ring.

if the colours match then your all good. I'm almost positive that its blue for 21mm... 

 

mine had a blue ring round ball joint gator and where 21mm cheers still dropped and measured before buying new ones took 2.5 hours with a cuppa in between