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Gray rectangular portable SSD with retractable USB-C and USB-A connectors

MemoStone

MemoStone US4-256 256GB portable SSD

SKU CH-GMZ5-RVGC3

A dual USB-C and USB-A portable SSD with 256 GB capacity, 3D NAND storage, and read speeds up to 540 MB/s

  • Total capacity256 GB
  • Sequential read speedUp to 540 MB/s
  • Sequential write speedUp to 480 MB/s
  • Interface typeUSB 3.1 Gen2
  • Form factorType C & Type A
  • NAND flash type3D NAND

Capacity US4-256

  • 256GB capacity stores large media libraries
  • USB 3.1 Gen 2 delivers 540 MBps read speed
  • Dual Type-A and Type-C connectors work with any device
  • 1,000,000-hour MTBF ensures long-term reliability
  • 100g pocket-sized design fits in any bag

MemoStone US4-256 256GB Portable SSD

The MemoStone US4-256 is a 256GB external solid-state drive built around 3D NAND flash memory. It connects via USB 3.1 Gen2 and includes both a USB Type-C and a USB Type-A connector in a single housing. The drive weighs 100g and measures 85.2mm by 20.5mm by 8.0mm. It is suited for users who need fast, portable storage across devices with different USB ports.

For users needing dual-connector flexibility

This drive suits anyone who moves files between newer Type-C laptops and older Type-A desktops without carrying adapters. Sequential reads reach up to 540 MBps and writes up to 480 MBps, which handles large media transfers quickly. Buyers who need hardware encryption, ruggedised IP-rated casings, or capacities above 256GB should look at other models. The operating range of -5°C to 60°C covers typical office and travel use.

USB 3.1 Gen2 interface with 540 MBps peak read

The single specification that decides fit is the USB 3.1 Gen2 interface rated for up to 540 MBps sequential read and 480 MBps sequential write. Your host port must support USB 3.1 Gen2 (10 Gbps) to reach these speeds; older USB 3.0 or 2.0 ports will limit throughput. The 2.15W active power draw is supplied entirely by the bus, so no external adapter is required.

How it compares

Measured against everything we stock in Portable USB SSDs, at today’s prices. Recalculated every night.

Price $27.99
Cheaper than about 97% of the 410 comparable items (median $202.99).
Total capacity 256 GB
Lower than about 95% of the 311 comparable items (median 1 TB).
Sequential read speed Up to 540 MB/s
Lower than about 87% of the 157 comparable items (median 1,050 MB/s).
Price per TB $109.34 per TB
Cheaper than about 70% of the 310 comparable items (median $142.00 per TB).

New to this? Buying memory and SSDs with crypto — what to check, what it costs to pay, and what is never asked for.

Specifications

Product
Brand nameMemoStone
Product lineUS4
Model nameUS4-256
Part numberUS4-256
Total capacity256 GB
Product colorGray
Performance
Sequential read speedUp to 540 MB/s
Sequential write speedUp to 480 MB/s
Storage
NAND flash type3D NAND
Ports & slots
Interface typeUSB 3.1 Gen2
Power
Active power draw2.15 W
Size & build
Form factorType C & Type A
Overall width85.2 mm
Product depth20.5 mm
Overall height8.0 mm
Product weight100g
Environment & compliance
Operating temperature range-5 °C to 60 °C
Storage temperature range-20 °C to 75 °C
Operating humidity range5-95%
More details
Mean time between failures1,000,000 h

Other versions of this model

3 more in the same range

Questions about this item

How fast will the 540 MB/s read speed actually be when I copy files to my laptop?

You will see up to 540 MB/s sequential read and 480 MB/s write on a USB 3.1 Gen 2 port; speeds drop on older USB ports.

What does the USB 3.1 Gen 2 interface mean for real-world transfer limits?

The USB 3.1 Gen 2 connection caps at 10 Gbps, so the drive's 540 MB/s read and 480 MB/s write are the practical ceiling.

Will the 85.2 mm by 20.5 mm dual connector fit beside other ports on my ultrabook?

The drive measures 85.2 mm long, 20.5 mm wide and 8.0 mm thick; allow a little extra clearance for the flip-out Type-A plug.

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