WD40EFPX Labeled as WD40EFBX – What’s Going On?

If you’ve purchased a Western Digital hard drive—specifically the WD40EFPX model—and noticed that the label or the drive itself identifies as WD40EFBX, you’re likely confused about the discrepancy. Both model numbers appear similar, but they indicate different product lines and characteristics. So why does this happen, and what should you know if you're seeing this mismatch?

Understanding WD Model Numbers

Western Digital (WD) uses a structured model naming convention for its drives. Here’s a basic breakdown:

WD40 = 4TB capacity

EFPX and EFBX = Internal model designations indicating certain characteristics, such as cache size, RPM, intended use (NAS, desktop, surveillance), or manufacturing batch

For example:

WD40EFPX is typically listed as a WD Red Plus NAS drive, 5400 RPM, with CMR (conventional magnetic recording).

WD40EFBX is commonly associated with WD Red Pro, usually 7200 RPM, also using CMR and designed for heavier NAS workloads.

Why the Labeling Confusion?

There are a few reasons this model mix-up can occur:

1. Firmware or OEM Rebranding

Sometimes, a drive physically labeled as WD40EFBX might contain firmware matching the WD40EFPX specification. This is especially common with OEM drives supplied to system builders or NAS manufacturers like Synology or QNAP. WD may repurpose similar internal hardware with slight firmware tweaks and assign different model numbers based on intended use.

2. Packaging vs. Drive ID

It’s also possible the external packaging (box) lists the drive as EFPX, while the drive’s internal firmware or system information (e.g., via CrystalDiskInfo) reports it as EFBX. This discrepancy can arise from using shared hardware platforms between model lines.

3. Inventory or Supply Chain Substitution

In some cases, Western Digital (or a retailer) might ship an equivalent drive as a replacement or under a similar SKU due to supply constraints. If the EFBX model meets or exceeds the performance specs of the EFPX, it could be supplied as a drop-in substitute, especially during RMAs.

What’s the Difference Between WD40EFPX and WD40EFBX?

Feature WD40EFPX WD40EFBX

Intended Use NAS (WD Red Plus) NAS (WD Red Pro)

RPM 5400 7200

Cache 128MB or more 256MB or more

Drive Type CMR CMR

Warranty (Retail) 3 Years 5 Years

Workload Rating ~180 TB/year ~300 TB/year

If you're looking for quiet operation and energy efficiency, the WD40EFPX is better suited. For faster performance and heavy NAS usage, the WD40EFBX (Red Pro) is ideal.

What Should You Do?

If you receive a drive with this labeling discrepancy:

Check the specifications using software like CrystalDiskInfo (on Windows) or Smartmontools (on Linux/macOS).

Compare actual performance (RPM, cache, throughput).

If the performance matches or exceeds what you paid for, you may not need to worry.

However, if you purchased the drive for specific characteristics (like low power draw or noise), consider contacting the seller or WD support for clarification or exchange.

Final Thoughts

The WD40EFPX vs. WD40EFBX label confusion highlights the complex nature of WD’s product lines and supply logistics. Always verify the actual drive specs using system tools if model numbers don’t match. Knowing the real capabilities ensures you’re getting what you paid for—whether you’re building a quiet NAS or a high-performance RAID array.