IWISS SN-025: Another head scratching “DuPont” crimp tool lands

Following on from my recent review of the Preciva PR-3254 crimp tool, I hit up eBay and Amazon to see if any other such tools may have surfaced lately. I found one:


We have a new tool (Amazon UK link), which is also apparently specifically designed for these contacts. At the time I wrote this article, the SN-025 is not (yet) listed on IWISS’s website?

A little bit of context

Left: The jaw of a typical budget tool. Right: SN-025

SN-025 is a particularly unusual crimp tool because it has ‘O’ shaped insulation crimpers. Some contacts (for example “DuPont” type) require a tool like this for correct crimping however historically almost no generic hand tools with this type of die had been available.

In the decades since imitation DuPont Mini-PV connectors first surfaced, hobbyists instead had to resort to mutilating contacts in unsuitable tools like the one above on the left. Only those in possession of either the DuPont-designed hand tool (extremely expensive) or the appropriate automated applicator had been able to crimp them correctly.

Two contacts apparently crimped with the IWISS SN-025. A “DuPont” contact, and, err, what’s that other one? Recognise it? please drop a comment.

The above graphic is provided by the Amazon seller, specifically pointing out that it wraps the insulation around the wire. It’s almost as-if they’ve been reading my crimp connectors page

While this is being sold as a “DuPont” crimp tool, it appears it is predominantly designed for another type. “Superseal” connectors are frequently mentioned in the context of this tool. It has three dies:

  • AWG 28 for “DuPont” contacts?
  • AWG 20 for mystery larger contact
  • AWG 18 for mystery larger contact

The AWG 28 die

DuPont HT-95. The gold standard which I’ll be comparing against.

Let’s put some “DuPont” contacts in there and see what we end up with:

Of course SN-025 wasn’t going anywhere near the HT-95’s crown as ultimate “DuPont” crimp tool but it did do marginally better than the Preciva PR-3254 I reviewed previously.

The SN-025 not having an AWG 24 die, it over-crimped the insulation as we would expect, and the wire part isn’t crimped anywhere near as tight as it is supposed to be – typical for Chinese tools.

If we were to cut open the wire parts of the DuPont vs IWISS crimps, we would find something like this. For the SN-025, likely a lot worse. Source: TE Connectivity

The other two dies?

The marketing image typically attached to this tool features a mystery contact crimped onto AWG 22 wire. Whatever it is, I don’t have one, but it doesn’t matter because I’m only looking at the crimps. Let’s put some AWG 22 wire and a similar sized contact in the AWG 20 die and see if we can re-create it:

Nope. The insulation crimp is far too loose, not gripping at all, so that picture is hogwash. Let’s see what else we could potentially use those dies for…

I went through my crimp tool cupboard to see if I had any others like this. Of the, err, considerable number (I’ve lost count) of manufacturer original tools in my collection, just seven have an ‘O’ type insulation crimp. Only two of those were in this wire size range:

Top: TE Multimate crimp tool. Bottom: TE Economical Interconnect crimp tool

TE Multimate

An interesting type to compare against because Multimate contacts look quite similar to the one pictured in the image the tool is sold with. This tool may be designed for use with a similar type of connector of Chinese design/origin. Given how esoteric these are, no point in going any further into that.

Economical Interconnect

A common type stretching to AWG 20 wire size, which has an ‘O’ crimp. More about these here.

KK .396 (?)

Lost in translation? The range of contacts apparently crimped by this tool.

In addition to the “DuPont” types, Molex KK .396 (.156″) is offered as a supported contact type. Not something the average hobbyist is going to be reaching for. I’ve got the manufacturer original tool for these, it’s not quite an ‘O’ type crimp, but let’s give it a shot anyway:

Mini-Fit Jr (?)

The die in the manufacturer original tool is quite similar to the KK .396 tool, so we’ll look at these too.

Certainly not one for E.I. It was OK on the wire part but it didn’t touch the insulation crimp.

For KK .396. Pretty good! the insulation part is a smidgen too loose on AWG18 wire, even when crimped in the AWG 20 die (forget it for AWG 20 wire). The results do not match the marketing image, I can only assume that was done by a different tool. Or, perhaps, the marketing image is depicting a smaller KK .254 contact?

Last but not least, the results for Molex Mini-Fit Jr looked quite good, so I’ve taken a closer look:

AWG 18 wire crimped by 3 tools. On the left a typical result of a budget tool, with the insulation deeply pierced due to the very long tabs on these contacts.

For the SN-025 crimp on the right: It takes a bit of practice, and the lack of a bell mouth has cut the wire a little, but otherwise the SN-025 has yielded a result very similar result to the Molex 63819-0900, correctly and cleanly wrapping the insulation support. The SN-025 doesn’t have the needed asymmetry in the insulation crimper to allow the tabs to easily fold over each other, but it they seem to most of the time when I tried it.


The seller I purchased this from didn’t mention Superseal in the listing, but others do. This is potentially what the larger two dies are designed for. I don’t use these.


Without a specification from the manufacturer, and subsequently knowing what it was actually designed for it’s difficult to give it a final judgement. Wire crimping force is quite respectable for larger contacts i.e. KK.396 / Mini-Fit Jr, but not so great for “DuPont” contacts.

As always my recommendation is that this tool (and any other tool in this price bracket) should only be used for applications in the “fun” category, specifically the kind of fun that doesn’t involve someone losing an eye when it goes wrong.

Manufacturers of tools around this price do not spend any time ensuring that the tools they produce crimp contacts to the specifications of a specific type, instead they are a broad brush design intended to crimp a range of contacts to a vaguely presentable standard. Yes we’ve got some nice crimps on Mini-Fit Jr, but that is purely luck, and only achievable with very specific contact placement during crimping.

If you’re building something critical and/or expensive, name brand contacts and the manufacturer tool should be used. I have detailed a lot of these on this page.

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