A total of 4x M.2 can be installed on the board. Important note: The new Asus mainboards use a so-called Q-Latch to lock the M.2. These are cheap plastic parts and there is no possibility to use the small M.2 screw for this anymore. Because of this retrograde development, not all M.2 hard drives with heatsink can be locked on new (and expensive) Asus boards! Manufacturers such as Gigabyte also have these new Q-latches but you can still use the M.2 screw to fix them. If you want to avoid this experience when building a new PC, better NOT buy an ASUS MAINBOARD. Because of this completely unnecessary and retrograde development, all Asus boards should be sent back to Taiwan immediately.