The Extrema Ratio AERO FX Nitrogen Mud Orange combines the minimalist design of the small Italian EDC fixed-blade knife with a colour scheme particularly suited to the brand’s outdoor ethos.

The handle features the ‘Mud’ finish here – a subtle earth-tone colour enhanced by an orange accent that deliberately draws the eye to the central section of the knife. More understated than the Blue Orange version and distinct from the classic Forest Green, this configuration has a particularly striking character.

The AERO FX is built on a heavily skeletonised full-tang construction. Extrema Ratio has sought to remove as much material as possible to achieve an extremely flat and lightweight knife without sacrificing the robust feel characteristic of its products.

Its blade is made from Nitrogen steel and features a MIL-C-13924 blued finish. Extrema Ratio combines this steel with good corrosion resistance, effective edge retention and relatively simple maintenance.

The handle is made from Anticorodal aluminium. The AERO FX’s attachment components can be replaced, allowing the colour scheme to be changed at a later date.

The carrying system is particularly comprehensive. The main Kydex sheath has an extremely slim profile, whilst a second Kydex attachment point offers additional mounting options. Paracord and twin cut-resistant rubber loops for horizontal carry are also supplied.

Technical specifications for the Extrema Ratio AERO FX Nitrogen Mud Orange fixed-blade knife:
Brand: Extrema Ratio
Model: AERO FX
Version: Nitrogen Mud Orange
Made in: Italy
Type: EDC fixed-blade knife
Construction: skeletonised full tang
Total knife length: 19.1 cm
Blade length: 8.0 cm
Handle length: 11.1 cm
Blade thickness: 4.8 mm
Steel: Nitrogen
Blade finish: MIL-C-13924 burnishing
Grind: flat
Handle: Anticorodal aluminium
Handle colour: Mud
Detail: Orange
Handle components: interchangeable
Claimed weight: 92 g
Sheath: Ultra-thin Kydex
Accessories included: additional Kydex interface, paracord and double loops for horizontal carry

Tellknives review:
The Mud Orange version is perhaps the colourway that strikes the best balance between the two personalities of the AERO FX; the ‘Mud’ retains the outdoor and operational references traditionally associated with Extrema Ratio, whilst the subtle touch of orange clearly positions the knife within the AERO range’s new, more contemporary and aesthetic approach.

The technical concept remains equally interesting: Extrema Ratio isn’t simply seeking to produce a small fixed-blade knife. The skeletonised construction, the extremely slim carrying system and the interchangeable components show that the AERO FX has genuinely been developed with EDC use in mind.

And despite this focus on lightness, the brand has not sought to completely erase its DNA. The blade retains deliberately robust proportions, and the full-tang construction lends a genuine sense of solidity to a knife designed to practically disappear when carried.

When it comes to the different colourways, the choice is essentially a matter of aesthetics. For us, Mud Orange is probably the most versatile: distinctive enough as an Extrema Ratio model to appeal to fans of the brand, yet original enough not to look like yet another run-of-the-mill small tactical fixed-blade knife.