The Black Lime is one of the AERO FX variants that most boldly plays on contrast. Here, Extrema Ratio combines a very understated black handle with a lime-coloured central element, known as ‘Lime’, which is particularly vibrant and thus gives this small fixed-blade EDC knife an instantly recognisable identity.

Beneath this contemporary design lies the original AERO FX construction: a heavily skeletonised full-tang architecture, developed to reduce the knife’s weight and thickness whilst retaining a particularly robust structure.

The blade is crafted from Nitrogen steel and features the MIL-C-13924 bluing finish characteristic of many Extrema Ratio models. Its flat grind and compact size make it a knife designed primarily for everyday cutting tasks.

The black Anticorodal aluminium handle retains the interchangeable component system unique to the AERO FX range. The ‘Lime’ detail thus becomes a striking graphic feature at the centre of an almost entirely black design.

The carrying system is an integral part of the design. The AERO FX comes with a particularly slim Kydex sheath, as well as various accessories to adapt how it is carried for everyday use.

Technical specifications of the Extrema Ratio AERO FX Nitrogen Black Lime fixed-blade knife:
Brand: Extrema Ratio
Model: AERO FX
Version: Nitrogen Black Lime
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: black
Detail: File
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:
Extrema Ratio could easily have produced the AERO FX solely in its usual military colours. This Black Lime version demonstrates precisely that the project is aiming for a different market, just like the Black Orange version.

The black immediately retains the brand’s identity, but the lime completely breaks with the usual austerity of its knives. On such a compact piece, this small splash of colour is enough to visually transform the whole design.

We find the result particularly well-suited to an EDC. It remains discreet enough for everyday carry whilst being instantly recognisable when taken out of its sheath.

We’re also intrigued by the AERO FX’s design due to its focus on lightness. Extrema Ratio hasn’t simply made the knife thinner: the full-tang structure is extensively hollowed out and complemented by minimalist, interchangeable handle components.

The result therefore retains something very ‘Extrema Ratio’ whilst clearly moving away from its traditional military designs.

Of the various colourways, Black Lime is probably the most contemporary and striking. For those who love Extrema Ratio but want to move away from the usual Black, Green or Desert, this is certainly one of the most interesting versions of the AERO FX.