Entering a special E3 promo code on EA's Origin service unlocks the Close Quarters DLC pack for Battlefield 3.

To get your free content pack, launch Origin and select "Redeem Product Code..." under the Origin menu on the top bar. Enter "BF3E3" (without the quotes) and you should unlock the Close Quarters pack.

Read more here: https://www.gameinformer.com/b/news/archive/2013/06/14/battlefield-3-close-quarters-dlc-free-on-pc.aspx

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