Battlefield 3 owners can currently download the 'Close Quarters' multiplayer map pack for free with the use of an E3 promotional code.
EA has made the content free to PC and console players in conjunction with this week's E3 expo.
According to Game Informer, you can unlock the DLC free by launching the Origin client, and via the "Redeem Product Code" menu enter the code 'BF3E3'.
It's unclear when the promotion will end but E3 concluded yesterday, so we'd suggest you take advantage of it ASAP.
DICE debuted Battlefield 4's highly-anticipated multiplayer gameplay at E3 this week, and you can get CVG's impressions in this Battlefield 4 multiplayer preview.
You can also check out new videos of both the single- and multiplayer modes here.