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OWC Mercury
On-The-Go™ Pro

640GB USB 3.0 Storage Solution

Mac / PC / USB 3.0, 2.0 & 1.1
  • Mac
  • PC
  • USB 3.0
The OWC Mercury On-The-Go USB 3.0 Storage Solution provides maximum storage in an ultra-portable, totally bus powered design!
Stylishly engineered in a sleek, impact-resistant acrylic enclosure, the Mercury On-The-Go Pro incorporates shock-isolation technology to give maximum protection for your precious data inside. The Mercury On-The-Go Pro is a true must-have for users like you who are seeking High-Performance and Highly Reliable storage weighing less than 11 ounces and that is small enough to fit in your pocket.
Outstanding Features
Compact and Versatile
If you're looking for one of the most compatible mass storage solutions made, look no further! The OWC Mercury On-The-Go drive is all you'll need! The OWC Mercury On-The-Go has what it takes to truly work cross platform. The Mercury On-The-Go Pro is bus-powered, so it doesn't require an AC adapter!
Cool and Silent
The OWC Mercury On-The-Go's fanless design offers near silent operation while still keeping your drive cool. The built-in aluminum heatsink underneath the drive and passthrough cooling vents on the top of the case work in tandem to provide optimum results. 
SuperSpeed Ready, Yet Backward Compatible
The OWC Mercury On-The-Go can be used with any Macintosh or PC with a USB 3.0/2.0/1.1 port. Now you can have SuperSpeed performance up to 500MB/s and compatibility with legacy machines!


  • OWC Mercury On-The-Go Pro USB 3.0 & 2.0 storage solution
  • High Quality Double Shielded USB 3.0 & 2.0 certified connecting cable
  • Carrying Case
  • Assembly Manual & User Guide


Product Specifications:

Bus Interface

  • USB 3.0 / 2.0 & 1.1 Backwards compatible port.


  • ASMedia 1051e USB 3.0 chipset

Standard Mechanism

    640GB HGST Travelstar™ 5K750 Specifications:


    Form Factor
    2.5″ HDD
    SATA 3.0Gb/s NCQ
    Formatted Capacity2
    Rotational Speed
    5,400 RPM
    Cache / Data Buffer
    Manufacturer Model Number
    RoHS Compliant


    Height (max)
    9.5mm (0.370″)
    Width (max)
    69.85mm (2.750″)
    Length (max)
    100.35mm (3.951″)
    Weight (typical)
    102g (0.225 lbs.)
    Data Heads
    Number of Disks
    Guaranteed Sectors
    Bytes per Sector
    Areal Density


    Load/Unload cycle


    Transfer Rate (Max)
    996 Mb/s
    Track-to-track Seek
    Average Seek Time
    Average Latency


    Maximum Start Current, DC
    4.5 Amps
    Seek Power
    1.7 Watts
    Read Power
    1.4 Watts
    Write Power
    1.4 Watts
    Idle Mode
    1.5 Watts
    Idle Mode, Active
    0.8 Watts
    Standby Mode
    0.2 Watts
    Sleep Mode
    0.1 Watts

    Environmental (Operating)

    400 G max at 2ms
    Ambient Temperature (°F)
    32°F to 140°F
    Ambient Temperature (°C)
    0°C to 60°C
    -304.8 m to 3,048 m (-1,000 ft to 10,000+ ft)

    Environmental (Non-Operating)

    1000 G max at 1ms
    Ambient Temperature (°F)
    -40°F to 149°F
    Ambient Temperature (°C)
    -40°C to 65°C
    -304.8 m to 12,192 m (-1000 ft to 40,000+ ft)


    Idle (Typical)
    2.4 bels
    Seek (Typical)
    2.6 bels
    1. 1GB = 1,000,000,000 bytes. Total accessible capacity varies depending upon operating environment (typically 5-10% less). The actual total capacity will depend on your own defined file settings/preferences.
    2. In terms of standard gigabytes, 1GiB ≈ 1.074GB and refers to the actual formatted capacity of shown under Mac OS 10.5 or earlier and Microsoft Windows OS.
    3. Specific application environments such as temperature and duty cycle will affect the overall reliability rates.
  • 640GB* HGST Travelstar 5K750**

  • *1GB = 1,000,000,000 bytes. Total accessible capacity varies depending upon operating environment (typically 5-10% less). The actual total capacity will depend on your own defined file settings/preferences.

    **OWC reserves the right to replace or upgrade to equivalent or better components.

Drive Interface

  • SATA (Serial ATA) Revision 3.0

Drive Cache Size

  • 8 Megabyte (8,192k)

Drive Rotation Speed

  • 5400RPM

Max Data Transfer Rate

  • USB 3.0 - 500MB/s
  • USB 2.0 - 60MB/s

Port/Interface Bootability

  • Can I use this solution as an external startup drive?
  • USB 3.0: Supported on Macs and PC's meeting minimum requirements. - Click for more info
  • USB 2.0: Supported on Macs and PC's meeting minimum requirements. - Click for more info


System Requirements

  • Macintosh: Macintosh OS 8.6 to 9.2.2, OS X 10.2.x or later including ‘Lion’ 10.7.x, and an available USB 3.0 port. Time Machine® Compatible: Mac OS X 10.5 (version introduced) and later.
  • PC: Windows Vista, XP, 2000, NT, 98, and an available USB 3.0 port.
  • Linux: Linux compatible via supported the USB interface.

Power Supply*

  • Bus Power via USB on most computers with USB 2.0 port factory stock.
  • Optional AC Adapter* (available as a separate purchase here)

  • * AC adapter not required for most applications provided computer bus supplies appropriate power needs.

External Case Dimensions

  • 3.5" (W) x 5.5" (D) x 1" (H)
  • 88.9mm x 139.7mm x 25.4mm

Total Shipping Weight

  • Less than 10.1 oz. (.28kg) with drive, 6.8 oz. (.19kg) bare enclosure

Operating Environment:


  • (operating) 5°C - 55°C (41°F - 131°F)
  • (non-operating) -40°C - 65°C (-40°F - 149°F)

Relative Humidity

  • (operating) 8% - 90% RH (Non-condensing)
  • (non-operating) 5% - 95% RH (Non-condensing)


  • (operating) 70G 2mS;
  • (non-operating) 175G 2mS


  • (operating) 1.0G (5 - 300Hz)
  • (non-operating) 5.0G (5 - 500Hz)


  • More than 300,000 power-on hours

Load/Unload Cycles

  • 600,000
Manufacturer provided specifications for Other World Computing p/n MSU35640GB8 UPC#: 812437029772


Click any of the benchmarks below to view the results.
macOS Test Results
Windows Test Results


Customer Ratings

Write a Review 4.8 / 5 118 out of 127 (93%) reviewers would recommend this product
1 2 3 4 5 6
Verified Buyer
Reviewer: TonyB Location: Perth WA Age: 35-44 Experience Level: Power User Owned Product: less than a month
Rating: 3/5 Disappointing June 30, 2012 Having ripped out many a hard drive from all sorts of computers and also having set up plenty of portable bare hard drives I found this kit to be disappointing and difficult. The instructions are split into two separate documents neither of which fully cover the installation process. Normally this wouldn't be a problem because this kind of installation should be straightforward. However, the SSD hold down screw was too long such that it wouldn't firmly hold the SSD in place and the other screws were too short to hold the bridge card in. Luckily it seems to fit in quite snugly without any screws. But if the ultimate test is does it work? - Well yes. Is it blazingly fast? - No not really. With an OWC 500GB SSD in there it certainly doesn't achieve the 500MB/sec max speeds claimed for USB3.0 nor the 200MB/sec for the SSD. I transferred 150GB using USB3.0 in 31 minutes (which by my calculations is about 80 MB/sec). I did exactly the same test onto another brand's USB3.0 5400RPM SATA 2.5" HD and it took 46 minutes. Did the same onm a USB2.0 5400RPM SATA 2.5" HD and it took 66 minutes. So I guess there are speed advantages but in the order of two times and no more.

This review is from OWC Mercury On-The-Go USB 3.0 External Enclosure for Apple MacBook Air 2010 & 2011 Flash Storage.

Response from OWC, Marketing July 2, 2012 This product was meant as a temporary solution to getting some use from the removed Apple drive on your 2010-2011 MacBook Air while a more customized solution was in development. The Mercury Aura Pro Envoy is that customized solution: http://eshop.macsales.com/item/OWC/MAU3ENVOY/ The second instruction booklet is to show what is different for installation of the MacBook Air SSD as opposed to a 2.5" hard drive that the On-The-Go line was designed for: http://eshop.macsales.com/shop/firewire/on-the-go Transfer speeds will vary depending on your setup, our marketing simply states the fastest theoretical speeds of the interfaces. The top speed limitation is always the lowest common denominator. For example, while USB 3.0 has a maximum speed to 500MB/s - the fastest MacBook Air stock SSD we've seen has a maximum speed of 200MB/s (some models were slower), so right off the bat, the top speed can only hit 200MB/s if you have the fastest SSD. Now, let's say you're plugging the device into a USB 2.0 port as found on the 2010-2011 MacBook Air models that the drive would be removed from and the theoretical maximum speed is then reduced to 60MB/s. The data itself can also be a determining factor on real world speeds. One large file transfers faster than a bunch of smaller files. It is kinda like driving - you can have a car that has a top speed of 200 mph, but if you're only driving a few feet at a time you're not reaching that full speed with each individual transfer.
Reviewer: apg028 Location: Hong kong Age: 25-34 Experience Level: Home User Owned Product: over 6 months
Rating: 5/5 I need it. Product is good April 19, 2012 I would recommend this item to a friend! This review is from OWC Mercury On-The-Go USB 3.0 External Enclosure for Apple MacBook Air 2010 & 2011 Flash Storage.
OWC 640GB OWC On-The-Go Pro Mfr P/N: MSU35640GB8 OWC SKU: OWCMSU35640GB8 USB 3.0 Storage Solution 3 Year OWC Limited Warranty
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