The Dell Precision M4800 Mobile Workstation Supports up to 3 Drives. (One 2.5" Solid State Drive or Hard Drive in the Easy Eject Drive Bay and/or One mSATA Solid State Drive in the WWAN Slot and One 2.5" Solid State Drive or Hard Drive in the Modular Bay Carrier) Note: The second 2.5" Drive is optional and is located in the optical drive bay when installed. If replacing the optical drive for a second 2.5" Drive, you will need the Dell modular bay drive carrier p/n MRR89 for installation. If installing a 2.5" Drive in the easy eject bay, you will need the 2.5" Drive easy eject bay caddy p/n 794WN for installation.