Serious professional photographers who demand one of the fastest most rugged and most durable memory cards on the market should choose the SanDisk Extreme III SD card. Built to work under the most challenging conditions with SanDisk Extreme III you?ll get more speed better performance and unmatched reliability. That?s because only SanDisk Extreme III memory cards feature innovative ESP Technology for the fastest speeds and highest performance. ESP stands for Enhanced Super-Parallel Processing. Simply put it means you are getting the fastest read/write speeds available an amazing minimum 20MB per second** sequential read and write speed speed you?ll definitely appreciate whenever you find yourself shooting and storing pictures in harsh environments extreme temperatures or at high altitudes.