Lexar D400, 256GB, Silver

The maximum data reading speed in Megabytes per second. It indicates who many Megabytes per second can be transmitted by the particular flash memory to the computer or another device. For example, 5 MB/s allows to send one high quality mp3 file or a digital photo within a second.

The maximum data writing speed in Megabytes per second. It indicates who many Megabytes per second can be "received" by the particular flash memory from the computer or another device. For example, 5 MB/s allows to "receive" one high quality mp3 file or a digital photo within a second.

The type of connection supported by the flash memory.

USB2.0 technically maximum bandwidth speed is 480 Megabits that are transformed into Megabytes and are within the range of 40 Megabytes per second in the operation in the real world. Therefore USB2.0 flash memories that can write and read data above 30 MB/s can be considered as maximum high-speed within the limits of this connection. 

For ensuring a higher operation speed the USB3.0 standard was introduced and this is currently available in new computers of average and expensive category and can ensure maximum ~4 Gigabit per second data transmission resulting in the data bandwidth of up to 400 Megabytes per second. However, it has to be admitted that for copying data at this speed the computer has to be equipped with the HDD or SSD with the writing or reading speed equal to or above the reading or writing speed of the flash memory and close to the USB 3.0 index.

USB2.0 and USB3.0 are retroactively compatible standards, i.e. USB 2.0 devices can be used with the USB 3.0 connection slots and vice versa. It just has to be taken into account that the slowest bandwidth will be used, i.e. USB 2.0