Western Digital · Ultrastar DC HC550 · 512e
WUH721818ALE6L4 is Western Digital Ultrastar DC HC550 18TB SATA-6G. 3 of its 4 segments are defined in Western Digital's published documentation and decoded below; for the rest we have not found a defining document, and they are marked as such. 1 live listing below.
| Segment | What it means | Source |
|---|---|---|
| WUH | Ultrastar DC HC series, helium-filled. | Western Digital |
| 721818 | Capacity and generation field. The leading digits encode capacity in the family's own scheme; each model's own specification sheet states its exact capacity. | Western Digital |
| ALE | SATA 6Gb/s interface, 512e sector format. | Western Digital |
| 6L4 | Not sourced - we have not found a Western Digital document defining this segment. | Not sourced |
We decode only what the manufacturer documents. There is a large body of community knowledge about the undocumented segments above, much of it probably right, and none of it published by Western Digital - so it does not appear in this table. A reading nobody can check does not belong in a column headed “what it means”. Grammar reference: Western Digital - Ultrastar model-number nomenclature.
WUH721818ALE6L4 is Western Digital Ultrastar DC HC550, a 18TB hard drive on SATA-6G. It uses the 512e sector format, which decides whether it will drop into an array or controller expecting the other one.
We currently track 1 live listing against this exact part number, offered both new and refurbished (the table shows each listing's cheapest offer), and the two frequently carry different warranty positions even when the part number is identical. 1 sibling part number is documented below - these are the numbers most often mistaken for this one, and the table marks which fields actually differ.
| Manufacturer | Western Digital |
| Family | Ultrastar DC HC550 |
| Capacity | 18TB |
| Interface | SATA-6G |
| Sector format | 512e |
| Product class | HDD |
These are the part numbers most often confused with WUH721818ALE6L4. The differences below come from the same vendor documentation as the decode above - where a field is not documented, the row leaves it blank rather than guessing.
| Part number | Capacity | Interface | Format | |
|---|---|---|---|---|
| WUH721816ALE6L4 | 16TB | SATA-6G | 512e | reference |
Amber cells differ from WUH721818ALE6L4; grey cells match it.
| Listing | Condition | Pack | $/TB | Price | |
|---|---|---|---|---|---|
| WD DC HC550 18TB SATA 512MB Enterprise | Refurb | single | $28.89 | $519.99 | Buy on Amazon |
A manufacturer part number does not imply a manufacturer warranty, and this is where part-number buyers lose the most money. OEM stock, integrator pulls and gray-market units all reach the market under the maker's own numbering. Retailers selling them sometimes state plainly that the manufacturer warranty is none; others simply do not mention it, which is not the same as it being covered.
Coverage attaches to the individual unit and its serial number, not to the part number. That means the only reliable answer comes from the manufacturer, about the specific drive you are being sold.
Ask the seller for the serial number before purchase, then enter it in Western Digital warranty checker. We link the tool rather than showing a result here, because the answer depends on the individual drive and only Western Digital can give it.
A seller warranty is a different promise from a different company. What each warranty tier actually covers · Verify on arrival
4 in-stock listings · same capacity and interface, any part number · ranked by live cost per tb, refreshed about once a day
| Drive | Capacity | Interface | Recording | Condition | $/TB | Price | |
|---|---|---|---|---|---|---|---|
| WD DC HC550 18TB SATA 512MB Enterprise WUH721818ALE6L4 | 18TB | SATA-6G | EPMR | REFURB | $28.89 | $520 | Buy on Amazon |
| MDD 18TB SATA 7200RPM 5yr Warranty MDD18TSATA25672E | 18TB | SATA-6G | — | REFURB | $28.89 | $520 | Buy on Amazon |
| MDD 18TB SATA 7200RPM Enterprise MDD18TSATA25672E | 18TB | SATA-6G | — | REFURB | $30.56 | $550 | Buy on Amazon |
| WD Red Pro 18TB WD181KFGX WD181KFGX | 18TB | SATA-6G | CMR | REFURB | $32.72 | $589 | Buy on Amazon |
Every 18TB drive we track, ranked by cost per terabyte.
Product pages for WUH721818ALE6L4: WD DC HC550 18TB SATA 512MB Enterprise · WD Ultrastar DC HC550 18TB SATA (no current offer). Each carries that listing's own condition, provenance and alternatives; the priced table above is in-stock offers only.
WUH721818ALE6L4 is Western Digital Ultrastar DC HC550 18TB SATA-6G. 3 of its 4 segments are defined in Western Digital's own published documentation - the decode table on this page shows each one with the document that defines it. For the remaining segments we have not found a defining document, and we say so rather than repeating a community guess as fact.
The part number cannot tell you - coverage follows how the unit entered the market, not its designation. Of the 1 live listing we track for WUH721818ALE6L4, 1 is sold new and the rest used or recertified, and only the new units can carry Western Digital's own cover. Check the specific serial with Western Digital's own tool, linked in the warranty section on this page.
WUH721818ALE6L4 and WUH721816ALE6L4 are both in the Ultrastar DC HC550 range. The clearest difference is capacity - 18TB against 16TB. The variant table on this page lists every sibling we document with what differs.
We track 1 live listing carrying this part number, shown above with condition and cost per terabyte; the cheapest sits under ASIN B08NWF1X6P. Prices come from Amazon US, re-checked about once a day per listing; the buy links go to the live listing because the price can change between our check and your click.