To make things slightly confusing there are three series of Sony XQD cards; S-Series, H-Series, and N-Series. The S-Series comes in two speeds (168MB/s and 180MB/s) and the new N-Series is 125MB/s. The H-Series is now discontinued (was 125MB/s). According to Sony; “the S-Series features a Wear Leveling Function, Error Correction Code, Data Refresh Function and other new features to enable secure and stable recording of 4K content, helping to meet the rigorous demands faced by professionals. The N-Series gives consumers an affordable entry-level option that supports consumer 4K shooting.”

Read the full article at XQD Cards for Sony F5 and F55 at DV Info Net (http://www.dvinfo.net/article/acquisition/sonyxdcam/xqd-cards-for-sony-f5-and-f55.html)