Facebook signed an agreement with Microsoft to acquire $550 million in patents, the companies announced on Monday. The patents were part of the $1.065 billion in patents Microsoft purchased from AOL earlier this month. Patent trading!

Microsoft took ownership of approximately 925 U.S. patents and patent applications in addition to a license to AOL's remaining patent portfolio of about 300 patents. Now, Facebook has taken possesion of 650 of those patents.

This leaves Microsoft with 275 of the original patents and applications it bought from AOL, and they will retain a licence to 640 of patents and applications now owned by Facebook. 300 in addition to the 300 or so AOL patents it gained a license to earlier.

“Today’s agreement with Facebook enables us to recoup over half of our costs while achieving our goals from the AOL auction,” Brad Smith, executive vice president and general counsel of Microsoft, said in the release.

Sources familiar with the details of the earlier deal told Bloomberg Businessweek  that Microsoft did not intend to keep all of the patents it acquired from AOL and that Facebook made a bid for those same patents before but their bid was too low.