This is either an 8GB or 16GB solid state hard drive, depending on availability. Call if you need to know which one is currently in stock. Most HP printers that shipped with this drive had the 8GB version, although 16GB will work just as well. These are working pulls that have been erased and ready to use in various HP Laserjet printers, for example HP Laserjet M551, M601, M602, M603 and many more. Replaces part# SDSA5AK-008G-1006 and similar. Installing and transferring firmware to the solid stated drive requires some know-how. HP printers that use solid state drives typically store firmware on the drive, which means when you install a replacement hard drive your printer will immediately display an error because there isn't any firmware on the drive. Typically you would need to first download the firmware from HP's website, then transfer it to a USB thumb drive and insert the thumb drive into the printer to transfer the firmware. The firmware is uploaded in the printer's preboot menu.