Nozzle holder with std USB stick compartment in the front, general use storage. Modified larger USB slots + added micro SD slots. 2 magnet retainers in base 10mmx4mm magnets required + 10mmx1mm diameter sticky mild steel bases (both Amazon), Firm enough not to be knocked off & easy to remove to bed level/maintenance. UPDATE: 2 Versions N4Pro & N4Max. Made depth deeper for N4Max nozzles & moved the magnet positions, to stop magnet from pushing USB stick out of pocket.