Sonnet

Sonnet eGFX Breakaway Box 350

Expert rating6 / 10

View on Full CompassView on sonnettech.com

Connection:: Thunderbolt 3
PSU:: 350W
GPU Fit:: Single-slot only
Noise:: Ultra-low-noise Noctua fan

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Manufacturer: Sonnet Last updated: 2026-09-12

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Sonnet eGFX Breakaway Box 350 Review

If you're looking specifically for a compact, quiet single-slot eGPU enclosure like the Sonnet eGFX Breakaway Box 350 rather than a full-size double-wide box,

it's built for exactly that: a smaller 350W supply, a single-slot card limit, and a Noctua fan tuned for quiet operation, which makes it the pick for lighter workloads like video editing acceleration rather than a top-end gaming GPU.

What It Actually Is

The Breakaway Box 350 is Sonnet's smallest and quietest eGFX enclosure, built with a 350W supply and a single-slot GPU limit rather than the double-wide support most of this category offers. Sonnet fitted it with an ultra-low-noise Noctua fan, and it originally shipped bundled with GPUs for Avid HDX video workflows where a quiet, compact accelerator mattered more than raw gaming power.

Comparison to Alternatives

Every other Sonnet box in this category, the 550, 650, and 750ex, supports double-wide cards and far more wattage, so the 350 only makes sense if your card is genuinely single-slot or you specifically want the quieter Noctua fan. Compared to the Sonnet eGFX Breakaway Puck's pre-installed compact GPU approach, the 350 still lets you pick your own card, just within a tighter single-slot, lower-power envelope.

Our verdict

Reviewed by Burooj Alam. Rated by us, not by users.

Expert rating6 / 10

A niche but well-executed pick for single-slot cards and quiet operation, not for gaming-class GPUs.

Best for

Video editors running single-slot acceleration cards for Avid HDX or similar workflows
Buyers who specifically want a quieter Noctua-fan enclosure
Compact desk setups where a full double-wide box is overkill

Not for

Any double-wide gaming GPU, since the chassis physically won't fit one
Buyers wanting real laptop charging power (only 15W here)
Anyone chasing high frame rates on a modern RTX card

Specifications

What these specs mean

Identity

Brand	Sonnet
Model Number	eGFX Breakaway Box 350

Connectivity

Connection Standard	Thunderbolt 3
Extra Ports	None onboard beyond the GPU's own outputs

Power & Compatibility

PSU Wattage	350 W
Host Power Delivery	15 W
Max GPU Length	220 mm
Cooling Type	Active, ultra-low-noise Noctua fan

FAQs

What are the key specifications of the Sonnet eGFX Breakaway Box 350 (Thunderbolt 3 / 350W PSU / Single-Slot GPU / Ultra-Low-Noise Fan / Compact)?

Key specs for the Sonnet eGFX Breakaway Box 350: Connection Standard Thunderbolt 3, Extra Ports None onboard beyond the GPU's own outputs, Cooling Type Active, ultra-low-noise Noctua fan, GPU Compatibility Single-slot cards, GTX 1050 Ti to mid-range single-slot workstation and gaming cards.

Who is the Sonnet eGFX Breakaway Box 350 (Thunderbolt 3 / 350W PSU / Single-Slot GPU / Ultra-Low-Noise Fan / Compact) best suited to?

Best suited to: Video editors running single-slot acceleration cards for Avid HDX or similar workflows; Buyers who specifically want a quieter Noctua-fan enclosure; Compact desk setups where a full double-wide box is overkill.

What are the drawbacks of the Sonnet eGFX Breakaway Box 350 (Thunderbolt 3 / 350W PSU / Single-Slot GPU / Ultra-Low-Noise Fan / Compact)?

Not the best fit for: Any double-wide gaming GPU, since the chassis physically won't fit one; Buyers wanting real laptop charging power (only 15W here); Anyone chasing high frame rates on a modern RTX card.