A good dock turns a laptop into a desk setup with one cable: screens, keyboard, mouse, network and charging all at once. The wrong dock gives you a monitor stuck at a low resolution, a laptop that slowly drains while "charging", or a second screen that never wakes up. Most of those problems come down to three numbers and one symbol, and you can check them all before you buy. We've just booked in a batch of more than 600 used docks, and the same problems kept showing up. Here is what to look for.
Quick answer
Match a dock to your laptop on four things: how it connects (USB-C, Thunderbolt, DisplayLink over USB, or a brand-specific connector), how many screens it runs and at what resolution, how many watts it passes to your laptop, and whether your laptop's port supports video. On a used dock, also confirm the correct power supply and host cable are included, because without them many docks won't power up or charge anything.
The four kinds of dock
| Type | How it sends video | Works with | Watch out for |
|---|---|---|---|
| USB-C (DisplayPort Alt Mode) | Laptop's own graphics over USB-C | Laptops whose USB-C port carries video | Not every USB-C port does video |
| Thunderbolt | Laptop's own graphics over Thunderbolt | Thunderbolt laptops; many work in a reduced mode on plain USB-C | Pricier; features may drop on non-Thunderbolt laptops |
| DisplayLink (USB-C or USB-A) | Compressed video handled by a driver | Almost any laptop, including older USB-A only models | Needs the DisplayLink driver installed |
| Brand-specific connector | Dedicated docking port | Only the laptop ranges it was designed for | Useless on other laptops |
Check 1: can your laptop's port carry video and power?
USB-C is just the shape of the plug. The port behind it may carry data only, data and charging, or data, charging and video. To find out:
- Look next to the port for a Thunderbolt lightning symbol or a DisplayPort symbol (a small rectangle with a notch). Either means video out.
- If there's no symbol, search the laptop maker's spec page for "DisplayPort Alt Mode", "Thunderbolt" or "USB-C with video".
- If the port carries no video, you can still use a DisplayLink dock, which sends the picture over ordinary USB with a driver.
Check 2: how many screens, and how sharp?
"Dual monitor support" on a box doesn't always mean two high-resolution screens. The Kensington SD4700P, the most common dock in our current stock, is a good example. It runs one screen at up to 2560x1600, but two screens at up to 2048x1152 each1. That's fine for two 1080p office monitors, and it is not a 4K dock, whatever some listings claim.
Mac owners need to check the laptop as well as the dock. The M1 and M2 MacBook Air drive only one external display natively. The M3 manages two external screens only with the lid closed, and the M4 and M5 support two with the lid open2. On an M1 or M2, a DisplayLink dock is the usual way to run two monitors2.
refurbished monitors to pair with your dock
Check 3: does it charge your laptop, and fast enough?
Look for the dock's Power Delivery (PD) rating, which is what it passes to the laptop. This is not the same as the wattage printed on the dock's own power brick.
- The Kensington SD4700P uses a 135W power supply but passes up to 60W to the laptop1.
- The Dell WD19 passes 90W to a Dell laptop with its 130W adapter, or 130W with the 180W adapter, but only 90W to non-Dell laptops either way3.
- The HP USB-C Dock G4 passes 60W according to HP's own specification, even though some resellers list it at 100W.
As a rule, the dock's PD figure should be at least the wattage of your laptop's original charger. Below that, a laptop may charge slowly or lose charge under heavy work.
Some docks don't charge the laptop at all. In our current stock that includes the Lenovo 40A7 (DK1522), Kensington SD3600, HP 3005pr and Wavlink WL-UG69DK1. They're fine if you keep your laptop charger plugged in, but check before you buy.
If you're choosing a laptop for a docked desk setup, our MacBook Air M1 guide covers its single-display limit in more detail.
Check 4: buying a used dock? Check what's in the box
Docks have no battery to wear out, which makes them a sensible used buy. The catch is usually what's missing, not what's broken. From the batch we've been working through:
- Power supplies and cables are often missing. Many used docks turn up with neither. Docks usually need their own specific power supply, so make sure the listing includes the right one or offers it as an add-on.
- Proprietary plugs matter. The Kensington SD4700P needs a 20V, 6.75A, 135W barrel supply. The Targus ACP77 series uses a Targus-specific DC connector that generic bricks don't fit, and it charges laptops through legacy barrel tips rather than USB-C.
- The label may not tell you the model. Dell docks marked "K20A001" could be any of six WD19 variants. We identify them by cable: one USB-C cable is a WD19 or WD19S; a Thunderbolt-marked cable plus an extra rear Thunderbolt port is a WD19TB or WD19TBS; two captive USB-C cables is a WD19DC or WD19DCS. No 3.5mm audio jacks means an "S" model.
- Some cables can't be swapped. Lenovo type 40AN covers two docks. The Workstation version uses a split, dual-headed cable and two power bricks, and without that cable it is close to useless.
What to skip
- USB hubs sold as "docks" that don't list a video standard, resolution or Power Delivery wattage. If the spec sheet doesn't say it, assume it doesn't do it.
- "4K dual display" claims without a stated resolution for each screen. Look for two figures, like the SD4700P's single and dual limits.
- A dock bought before checking your laptop's port. Two minutes with the spec page saves a return.
Buying from Buyer Area
We identify every dock by its exact model, not just the regulatory type on the label, and we tell you plainly whether a power supply and host cable are included. Like everything we sell, docks come with a 12-month warranty, 30-day returns and free UK delivery. If you're not sure a dock suits your laptop, send us the laptop model and we'll check before you order. Pair it with a laptop from our refurbished Windows laptops range.
FAQ
Will any USB-C dock work with my laptop?
Not always. Your laptop's USB-C port must support video (look for a DisplayPort or Thunderbolt symbol) for a standard USB-C dock to run monitors. If it doesn't, a DisplayLink dock works over ordinary USB with a driver. Also check the dock's Power Delivery wattage if you want it to charge the laptop.
Why won't my docking station charge my laptop?
Common reasons are a dock that doesn't offer charging at all, a Power Delivery rating below your laptop's charger, the wrong or missing power supply on the dock, or a USB-C port on the laptop that doesn't accept charging. Check the dock's PD figure against your original charger's wattage.
Can a docking station run two monitors from a MacBook Air?
An M1 or M2 MacBook Air supports one external display natively, so two monitors need a DisplayLink dock. The M3 runs two external displays with the lid closed, and the M4 and M5 support two with the lid open.
Is a used docking station worth buying?
Yes, if the seller confirms the exact model, includes the correct power supply and host cable, and offers a warranty. Docks have no battery to wear out, so the usual problems are missing parts and mislabelled models rather than faults.
Sources
- Kensington, "SD4700P USB-C & USB-A 5Gbps Dual 2K Hybrid Dock". https://www.kensington.com/p/products/device-docking-connectivity-products/laptop-docks-usb-accessories/sd4700p-usb-c-usb-a-5gbps-dual-2k-hybrid-dock-up-to-60w-pd-dp-hdmi-windowsmacos/ (checked 2026-09-16) ↩
- EveryMac, "MacBook Air Silicon Adapters and Displays". https://everymac.com/systems/apple/macbook-air/macbook-air-silicon-faq/macbook-air-silicon-video-ethernet-power-adapters.html (checked 2026-09-16) ↩
- Dell, "Dell Docking Station WD19 User Guide: Docking specifications". https://www.dell.com/support/manuals/en-uk/dell-wd19-130w-dock/wd19_userguide/docking-specifications?guid=guid-cd615eef-5015-4931-bf9b-e19f9cf50c4d&lang=en-us (checked 2026-09-16) ↩