Hard disk drive heights and polypropylene storage containers

Given how many hard disks I tend to have, I recently decided to purchase some anti-static polypropylene foam containers to store my drives.

Common retail outlets (Amazon and others) were selling these containers (which would hold between 10 and 24 disks) but for crazy prices: US$100, US$130, and US$150. And some other retail vendors want US$425.

The price was simply too steep; I wasn’t needing something brand new, used would be fine. So I turned to the one place where stuff like this tends to end up being sold for reasonable prices: eBay.

Before continuing I want to make something crystal clear: I am not shunning the eBay seller in any way. The seller was communicative, fair, and permitted me to return the products for a full refund. So please do not avoid purchasing things from this seller just because of my story — instead, you should be aware of what it is you’re actually getting (though I do wish the seller would update the product description to reflect reality).

Almost immediately I found exactly what I was looking for. Advertised as holding up to 25 3.5″ hard disks (quoting the product description: “They fit all 3.5″ hard drives”), they were perfect. Or so I thought…

I purchased 3 (only needed 2 but figured a spare might be useful). Shipping took about a week. I was thrilled once they arrived, but irritation ensued once I tried fitting drives in each slot: the majority of my drives wouldn’t fit properly.

It quickly became apparent to me what the issue was, and it was something that anyone unfamiliar with hard disk drives could have overlooked.

When it comes to 3.5″ hard disks, there are two flavours:

  1. Those which are 26mm (~1.072 inches) in height — these tend to be the majority (~90% of the time). An example would be the Western Digital WD3201ABYS,
  2. Those which are 20mm (~0.790 inches) in height — these are all single-platter and are intended to be used in thin/slim desktops, SFF PCs with limited height clearance, or certain models of 1U servers. An example would be the Maxtor STM3160815A.

Here’s a side-by-side photo of the above two drives so you can see the height differences:

Hard disk drives are always enclosed in anti-static bags for multitudes of reasons (static discharge possibly damaging the PCB, keeping dust off the interface connectors and PCB, and so on). Such bags tend to add between 1-2mm to a drive’s width and height. So effectively what you end up with is either 28mm or 22mm heights, respectively.

All 3 containers I received had slots which measured between 21mm (bottom of slot) and 23mm (top of slot) for drive height:

Insertion of a 26mm height drive required excessive force and would not fit all the way to the bottom of the slot — but worse, the foam dividers between slots would bend/warp, defeating the use of the slot next to it:

…while a 20mm height drive fit just fine (and with anti-static bag, fit snugly):

Based on what I can tell, these containers were originally used for storing and shipping 20mm height drives and were not designed for storing more commonly-found 26mm height drives.

Could I simply shove 26mm drives in and not care? Yes, but due to the bowing of the foam dividers this would effectively cut the total drive capacity in half (from 25 to 13). And the dividers would almost certainly (eventually) break/snap after being left stressed for long periods of time. Instead, a better choice would be to use the right tool for the job. :-)

Bottom line: vendors really need to go the extra mile and provide proper measurements when selling products for used with diverse products. It’s easy to overlook the fact that 6mm makes a world of difference.