If you can swing the $$, I'd order both sides. Arnott sometimes have a backlog of orders due to core shortage, so get them while you are still mobile and replace them when they finally let go. Only down side is you don't get your $ 100 core deposits back until you ship them the old shocks. Any competent mechanic should be able to replace these at ( 1 ) hour per side. You may need to go to someone who has BMW diagnostic computer to have ride height recalibrated. In my case, I was lucky and new shocks worked out level.