Kingston MicroSDHC memory card has write speed of approx. 5.4 MB/s whereas SanDisk MicroSDHC memory card has approx. 5.2 MB/s which are pretty close to each other. So, claim of both companies of minimum write speed of 4 MB/s on Class 4 MicroSD card is absolutely correct. Regarding Read speed, 20.7 MB/s of Kingston MicroSDHC card and 20.9 MB/s of SanDisk MicroSDHC card are almost similar.