2 different rear light part numbers?

[Feonuk]

Hi guys, I am looking at replacing a rear light on my 2016 a4 avant but am really confused as there appears to be two different variants?

Was wondering if anyone could help to explain the difference between them please.

8W9945091c (81500121)

8W9945091 (81500101)

 

They are both led I believe. 

Thanks in advance for any help

 

[Magnet]

Hello Feon, 

Thanks for being in touch with the forum. 
Wondered if you are considering buying from a main dealer or not? 
Kind regards,

Gareth. 

[Feonuk]

Hi Gareth, was going to try to save some cash and get some well looked after one's...

Will give audi a call and see if they can tell me the difference, thinking it could be to do with the dynamic side of things e.g 2016 model not having it? Might be wrong hey ho thanks for the help guys