1. Introduction

No MOLLE, but sold on its modularity? This is the system which sparked the micro chest rig revolution; spawning a febrile, comprehensive third party ecosystem, where the only limit to adaptability is the user’s imagination.

Spiritus made their reputation by making products for unoccupied niches and the Micro Fight is their flagship chest rig offering. Other companies talk about disruptive events and paradigm shifts, but it was Spiritus who came out of nowhere to totally change the narrative.

Over the last few years they’ve become massively popular, with an army of loyal fans based around their IG account, and a highly active Facebook appreciation group – The Spiritus Symptoms – started by none other than Chris from The Full 9.

Spiritus’ marketing is on point, often leveraging graphic design redolent of the 80s. As such, anyone who didn’t live through that decade may reasonably conclude that it was a very, very cool time. This nostalgia for the 80s leads me to what I think is a legitimate question for potential micro chest rig purchasers.

1.1 VHS or Betamax?

True initiates of the 80s will be familiar with the video tape format war. One of the reasons JVC’s VHS was the eventual winner is because the company would license its system to anyone who wanted it – meaning that the format was well supported by a lot of other electronics companies.

Twisting this aspect in to some sort of analogy, is the Micro Fight the VHS to everyone else’s Betamax? Spiritus has by far the most third party support. While I may not necessarily think the Micro Fight in its basic form (as featured in this article) is technically better than any other micro chest rig on the market; with its strategic modularity and broad spectrum ecosystem, the Micro Fight is way more customisable and therefore capable of more.

This represents the Micro Fight’s unique selling point: more opportunities for adaptability, and consequently the solid support it’s received from the likes of AXL, Microbat and Wild Bill – all contributing some very clever ideas.

And yet, fewer choices keep the user honest about what they need to carry; and also less likely to constantly change setups. So there are pros and cons to both outlooks.

1.2 Mk3 and Mk4 Chassis

I reviewed my Spiritus Systems Mk3 Micro Fight at the start of 2018 which, even then, was quite late in the day. Since then, Spiritus released a Mk4 version with marginal improvements (more like a Mk 3.1). I bought the Mk4 chassis recently to replace my Mk3, so thought it was time to refresh my review.

2. Micro Fight System Components

Rather than cherry picking from individual components which are sold separately, The Full Kit featured here is bought as a turnkey solution and represents Spiritus’ chest rig base configuration.

It consists of the following items:

  • 2.1 Mk4 Chassis
  • 2.2 556 Rifle Insert
  • 2.3 Full Flap
  • 2.4 Fat Strap and Back Strap

2.1 Mk4 Chassis

The Chassis is the Micro Fight system hub and the Mk4 revision differs only slightly from that of the Mk3.

When compared to the Mk3, the Mk4 exhibits:

  • A more expansive hook velcro field at the rear
  • An increased number of drainage grommets in its base*

*For use with Spiritus’ Universal Retention Kit (URK) to attach, for instance, an underslung TQ.

Mk4 Chassis
Mk3 Chassis

So, if you already own the Mk3 there’s little point in buying the Mk4 – unless you desperately want URK functionality.

On the reverse of the Chassis, the velcro field is one of the universal standards in chest rig design. Along with the top mounted integral male Fastex clips, it allows the chest rig to be attached as a placard to an appropriate PC.

Mk4 Chassis
Mk3 Chassis

Notwithstanding, in PC placard or chest rig mode, this velcro supports the attachment of Spiritus’ Expander Wings and/or a drop pouch such as the Spiritus SACK.

Here I’m using AXL’s SLAP to mount a Crye 6x6x3 GP as a drop pouch:

And here Ferro’s excellent The Mini Dangler, which complements the Micro Fight form factor perfectly.

The Chassis is divided into two, stepped, loop velcro-lined compartments.

These compartments have similar dimensions where it matters, in order to optimise the Chassis’ modularity.

That said, while the front compartment doesn’t extend quite as high as the rear, its base is higher.

This means that if a second 556 Rifle Insert is used to create space for six mags, the three mags up front will be slightly proud of the rear set. This helps, marginally, with extraction.

2.2 556 Rifle Insert

The Insert is composed almost entirely of elastic and accepts three 556 mags or other similarly sized objects. Hook velcro is attached to both sides, to secure it within the Chassis.

Readers may note that there’s no base to the insert. This is a slight drawback, because it means mag height cannot be determined by the user. It’s not a massive issue in use, but it is curious nonetheless.

Once secured within the Chassis, the insert forms mouths which remain open and receptive. It’s actually easier to reindex mags than it sounds, with a bit of care and practice. The difficulty increases when six mags are carried, however, as things are bunched up.

Of course, the user isn’t limited to 556 use and this is another massive selling point of the Micro Fight (which was unique until it was copied). It’s really easy to switch to a 417 mag insert or a sub-gun mag insert, for instance, just by swapping stuff around. These and other additional inserts are available separately.

2.3 Full Flap

Opening with a webbing tab, the Full Flap converts the Chassis’ front compartment in to a flapped GP pouch.

However, to do this the Flap must be secured by velcro into the rear Chassis compartment. velcro also allows the flap to be secured shut. Yet more velcro on the face of the Flap is colour-matched for morale patches, etc. Yes – Spiritus likes velcro.

A generous single utility pouch is a breath of fresh air. One flap, one sizeable opening to get my (massive) hand in – and velcro-in organisation that the user can buy separately if required.

Spiritus also produces a Half Flap, should the user wish to use half of the front compartment as a GP pouch and the other half to carry, say, an additional mag (they also make individual 556 mag inserts, as well as pistol mag inserts for this configuration).

Again, this is all part of the system’s modularity and is what sells the Micro Fight and powers its wider, third party ecosystem.

2.4 Fat Strap and Back Strap

With the addition of the included four female Fastex clips at the Chassis’ flanks, the Fat Strap shoulder harness and Back Strap are added for chest rig mode.

The Back Strap is nice and simple – just 1″ webbing, triglides and male Fastex clips. I’d like to see an elasticated version of this, as I’m rather used to the one which comes with my Crye AirLite Convertible Chest Rig.

Back Strap

An area where chest rigs so often fail, Spiritus’ strap system has been properly thought through. For a start, the Fat Strap is an H-harness (which I prefer to an X-harness).

Fat Strap

Secondly, it has a wide range of adjustment. Often, chest rigs straps are sized to work over a slick PC. Consequently, you find that some won’t cinch down effectively for use without armour – especially if the adjustment system is captive (feeds into itself, rather than leaving ends free). Luckily, Spiritus’ adjustment mechanism is free at the ends.

Thirdly, the Fat Strap has no padding, is flat and is just over 2.25″ wide; making it low profile and very comfortable. I don’t think I’ve once had it wander towards my neck where chafing can occur, nor has it impeded my sling.

As for details, the Fat Strap exhibits horizontal mounting platforms, composed of webbing or elastic. These can be used to route comms or hydration, for example.

The Fat Strap’s Chassis attachment points are also fully featured: the female Fastex clips are protected from knocks and held captive by elastic.

Being held captive, it’s really easy to connect everything without the clip flopping about. It also means that the portion of the strap which extends behind the Fastex clip doesn’t fold back on itself by accident, when donning the rig (unlike some competitor systems).

There’s also a loop field at the rear of the Fat Strap.

3. Micro Chest Rig Form Factor Notes

In chest rig mode the Micro Fight rides high and stays put. I think part of this is to do with the Chassis itself having such a small footprint: it seems that the wider the chest rig, the less conformal it becomes and the more it bounces with exertion. That may not be science fact, but it’s what I’m inclined to pursue until proved otherwise. I’ve noticed the same with other micro chest rigs, so this isn’t limited to the Spiritus.

Similarly beneficial, the Micro Fight’s form factor is such that the user’s sides are completely free of clutter. This is particularly useful when using a sling, for example, as there’s nothing for it to get hung up on. Again, this is a feature shared with all micro chest rigs, but it’s worth noting here.

4. Conclusion

It’s been two and a half years since my last Micro Fight review and in that time the platform has changed very little, because Spiritus pretty much got everything right with Mk3; Mk4 just finesses that idea.

What has shifted, radically, is the Micro Fight’s aftermarket of add-on modifications. And it’s this, along with excellent marketing, which I believe has allowed Spiritus to pull ahead of peer systems.

It’s no secret that in its base configuration (Mk4 Chassis; 556 Rifle Insert; Full Flap; Fat Strap and Back Strap) this is not my favourite micro chest rig. However, taken in the round – with all of its OEM and third party customisation options – the Micro Fight offers an unbeatable ecosystem.


Want more Spiritus Systems reviews? You can find a whole list of them here. The list is updated as more reviews are published.


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