An eGPU enclosure is a garage for a desktop graphics card, connected to your laptop by a single driveway. The host link is that driveway: Thunderbolt, USB4 or OCuLink decide how many lanes lead in and how fast traffic flows. The garage size and power supply decide which card fits and runs. Even the best driveway is narrower than a desktop's, so expect some performance loss. Check the driveway first, then make sure your card fits the garage.
How the enclosure connects to your computer: Thunderbolt 3, 4 or 5, USB4, or OCuLink, and the physical port it uses.
When it matters: Your laptop must have a matching port with PCIe support. Trap: a USB-C port without Thunderbolt or USB4 cannot run an eGPU even though the plug fits.
The Thunderbolt generation the enclosure supports. Thunderbolt 3 and 4 run at 40 Gbps, Thunderbolt 5 at 80 Gbps.
When it matters: Thunderbolt 3 and 4 give eGPUs the same PCIe bandwidth. Thunderbolt 5 roughly doubles it, but only when the laptop also has Thunderbolt 5.
The total speed of the cable connection in Gbps (gigabits per second).
When it matters: The headline number includes display and USB traffic. Only part of it carries PCIe data to the graphics card, so look at the PCIe tunnel spec too.
The PCIe generation and lane count that reach the graphics card through the cable, such as PCIe 3.0 x4 or 4.0 x4.
When it matters: A desktop slot gives a card PCIe x16. An eGPU gets x4 at most, and this is the main reason eGPUs run slower than the same card in a desktop.
Whether you can connect and disconnect the enclosure while the computer is running.
When it matters: Thunderbolt and USB4 enclosures support hot plug. OCuLink does not: plug in before booting, or the system may crash.
The real data speed between the computer and the graphics card, in GB/s (gigabytes per second).
When it matters: A better guide than the cable rating. Thunderbolt 3 and 4 enclosures land well below the 40 Gbps headline. Results also depend on the laptop's controller.
How fast a graphics card runs in this enclosure compared with the same card in a desktop, as a percentage.
When it matters: Expect a loss, larger with faster cards and at high frame rates. Using the laptop's own screen adds more loss than plugging a monitor into the graphics card.
The biggest graphics card the enclosure fits: length, height and thickness in millimeters, or in slots.
When it matters: Modern high-end cards are long and often 3 slots or thicker. Check all three dimensions and the power connector position against your card.
Whether a graphics card comes built in, which one, and whether you can replace it later.
When it matters: Built-in models are compact but fixed. Swappable designs let you upgrade the card while keeping the enclosure.
The outer dimensions and weight of the enclosure.
When it matters: Most enclosures stay on a desk. Compact models with built-in GPUs are easier to carry.
Skip it if it stays on one desk.
The power supply inside the enclosure, its wattage and its size standard.
When it matters: It must cover the graphics card and any laptop charging at the same time. A standard form factor PSU can be replaced or upgraded later.
The most power the enclosure can deliver to the graphics card, in watts.
When it matters: Compare this to your card's rated board power. Cards can spike above their rating, so leave headroom.
The power cables available for the graphics card: PCIe 8-pin plugs or the newer 12VHPWR (12V-2x6) connector.
When it matters: High-end cards need two or three 8-pin plugs or one 12VHPWR. Adapters are possible but add clutter and risk in a tight space.
How much charging power the enclosure sends back to your laptop over the same cable, in watts.
When it matters: Gaming laptops often need more than the enclosure supplies, so they drain slowly under load. Thin laptops usually charge fine at 60 to 100 W.
Skip it if you use the laptop's own charger.
How the enclosure cools the card and PSU, fan size and the rated noise level in dBA.
When it matters: Tight enclosures can make the card run hotter and louder. Larger, slower fans are usually quieter.
Skip it if you use headphones.
USB, Ethernet and storage ports on the enclosure, turning it into a dock.
When it matters: One cable connects the GPU, peripherals and network. Those ports share the same link, so heavy USB or network traffic can cut graphics bandwidth.
Skip it if you already have a dock.
Whether the enclosure is supported on Windows, the main platform for eGPUs.
When it matters: Works with both NVIDIA and AMD cards on Windows. Some laptops need a BIOS setting or updated Thunderbolt firmware first.
Whether the enclosure works on Mac.
When it matters: Trap: Apple Silicon Macs do not support eGPUs at all. Only older Intel Macs worked, and only with supported AMD cards.
Skip it if you use Windows or Linux.
Whether the enclosure works under Linux.
When it matters: Often works but may need manual setup for hot plug and display handling.
Skip it if you do not run Linux.
Whether the enclosure only works with certain laptops or brands.
When it matters: Some eGPUs use proprietary connectors tied to one maker's laptops or handhelds. Check your exact model is listed.