OWC Mercury Helios 3S Thunderbolt 3 PCIe Single Slot Expansion Chassis


  • Lightning-fast 40Gbps transfer speeds: (2) Thunderbolt 3 ports
  • Play your card: (1) PCIe (x16) slot for half-length, full-height, single or double-width cards
  • See more: DisplayPort 1.4 for connecting up to an 8K display
  • Easy card installs: No tools required
  • Charge while working: 85W of notebook charging

(Incl tax)
10 days
Delivery 4-10 days

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Mercury Helios 3S
Thunderbolt 3 PCIe Expansion Solution

Mac | PC | Thunderbolt 3| PCIe | DisplayPort
Use PCIe cards with your Thunderbolt 3 Mac and Windows PC
Maximize Your PCIe Card Investment with An External PCIe Slot
A New World of Expansion Flexibility
Using a video, audio, storage, network, or even gaming PCIe card with a Mac Pro or PC desktop is a simple matter of inserting your card into an open slot. But what do you do if you have a laptop or even a space-confined desktop like an iMac or Mac mini that doesn't contain a PCIe slot?
The OWC Mercury Helios 3S is an easy to use yet powerful expansion solution that adds an external PCIe slot to your Thunderbolt 3 equipped computer. Now you can maximize your existing PCIe card investment — or expand it! — while enjoying the flexibility of adding professional-class video production, transcoding, audio processing, data storage, and high-speed network connectivity to your machine.
Retask Without Limits

Instead of buying one or more function-dedicated Thunderbolt interface devices, you can use Mercury Helios 3S like a dock for multiple PCIe cards. Capture incredibly high-quality audio with a PCIe audio card and then retask Helios 3S with a PCIe SSD card to edit and archive tracks. You can swap cards in minutes, adding a new level of flexibility to your workflow.

Capture, Stream, and Share in Seconds
With dual 40Gbps Thunderbolt 3 (Thunderbolt 2/Thunderbolt backward compatible), the Mercury Helios 3S offers the bandwidth needed to support data-intensive 4K capture cards to speed up diverse video workflows such as vlogging. Boost your DAW with external DSP acceleration and run larger mixes with multiple plug-ins. Livestream the action in your gaming sessions or share files over a 10GbE or Fibre Channel network without any speed throttling.
Pro-Level Performance Cards for Every Need
Mercury Helios 3S supports a wide variety of half-length, full-height, single or double-width pro-level PCIe cards from leading brands like AJA, Apogee, ATTO, Avid Pro Tools, Blackmagic Design, CalDigit, HighPoint, Intel, Solid State Logic, Universal Audio, and OWC:
  • Video capture
  • Digital audio
  • Solid State Drive (SSD)
  • 40GbE/10GbE network adapters
  • SAS controllers
  • Firewire, USB, or eSATA host adapters
Add New Capabilities to Your Workflow
Thunderbolt 3 offers more than just speed. Mercury Helios 3S leverages the full power of Thunderbolt 3 to deliver added potential to your Mac or PC. Daisy-chain up to five additional Thunderbolt peripherals for incredible capabilities to work or play. Charge your notebook with 85W while you work. Even add another 4K monitor via the DisplayPort interface to expand your viewing space.
Plug and Play
No special software or drivers needed...just plug the Mercury Helios 3S into an open Thunderbolt 3 port on your computer with the included cable to immediately expand your system capabilities.

No tools required either...just remove two thumb screws and insert a card to start enjoying productivity gains wherever your work takes you.

  • Black
Windows PC Compatibility:
  • YES
Made in:
Designed, assembled and tested in the USA
3 Year OWC Limited Warranty

Product Specifications:

OWC Part Number



  • Black


  • Aluminum

OS Compatibility

  • macOS 10.13 or later
  • Windows 10 or later

PCIe Cards Supported

  • Mechanical: x16 slot and enclosure support cards up to half-length, full-height, and double-width
  • Bandwidth: PCIe 3.0 x4. Cards that require a minimum of x8 or more PCIe lanes are not supported. 
  • GPUs not supported
  • If the card requires a driver it must be Thunderbolt-aware.
  • Cards that require more than 75W are not supported.


  • Yes


  • (2) Thunderbolt 3
  • (1) DisplayPort 1.4


  • Thunderbolt 3: Titan Ridge (JHL7440)

Expansion Slot

  • PCI Express 3.0 interface (x4) with x16 physical slot

Display Host Capabilities

  • Supports dual display configurations via Thunderbolt 3 and DisplayPort
  • The DisplayPort does not support DP++
  • When using a DisplayPort to HDMI adapter, make sure to use an active adapter.


  • AC Input 2.2A 100-240V 50-60Hz
  • DC Output 12.5A 12V
  • Wattage 150W


  • Height: 8.2 cm (3.2 in)
  • Width: 14.3 cm (5.6 in)
  • Length: 23.3 cm (9.2 in)


  • 1.6 kg (3.64 lbs)


  • The Mercury Helios 3S can deliver up to 85W of power for host charging when the host is connect to the 85W port.
  • If the PCIe card installed uses more than 25W of power, plug in the power adapter to your host.
  • You can use the Thunderbolt 3 to Thunderbolt 2 adapter from Apple to connect this device to a Thunderbolt 2 computer. Power Delivery is not supported in this configuration and bandwidth will be limited to ~ 1375 MB/s.
  • Full DisplayPort 1.4 capabilities including 8K resolution depends on host computer support of DisplayPort 1.4 specification through its Thunderbolt 3 connection, host computer GPU capabilities, and connecting cable capabilities.

Manufacturer provided specifications for Other World Computing p/n HELIOS3S UPC#: 810586032773


  • (1) Mercury Helios 3S
  • (1) Thunderbolt 3 cable
  • (1) External power supply
  • (1) Power cable
  • (1) User guide