Sa microSD ang class rating is reference rana, dli na siya standard.. an original sandisk class 2 card can write as fast as 6-8MB/s thats class 6-8 for the reference.. the class 2 ultra mobile writes at a whopping 11-12mb/s pero class 2 rana siya rated. If sa mobile phone nimo gamiton ma bottleneck ka how fast the external slot can go. IMHO, anything that writes at 5-6mb/s minimum is already great.. mas impt para nako ang read speed.