With excellent minimum sustained sequentual write speeds, Advanced Memory Cards enable your camera to perform well in all modes including high-resolution video capture. ProMaster CFX-B cards use top quality flash memory and components for years of service and thousands of read/write cycles. Key features: 820 MB/s minimum sustained sequential write speed 3500 MB/s read speed CFX-B 4.0 PCI Express 4.0 Bus (also supports NVM Express) Heat & cold resistant Limited lifetime warranty