955 rear light cluster question

Hi all

I need a new rear light housing for my 2000 S3, and on the World of Triumph webpage there are two part numbers listed for the same housing (I only need the plastic housing/lens):

http://www.worldoftriumph.com/trium...p?block_01=&block_02=302753-0-2&block_03=9909

I spoke to World of Triumph and the 'SAE' version is for the US model of the S3 but is about half the price! He said I need the 'ECE' (European) version but couldn't actually explain why

Long shot, but does anyone happen to know what the difference might be?

 

Tidy, thanks for the advice