If you choose a class 10, beware that these cards are made for big data transfers and slow down the phone for app related Android operations. As the internal storage is small on E3, many of your apps will be on SD card and the data transfer that occurs on daily basis for such apps is small like less than 800 kb. Not all class 10 SD cards work well with these type of small transfers and hence slow down the phone. A good class 10 micro SD is the Samsung Evo 32 GB. Comparatively, it has proved to be faster than others in tests.
