Last tested

2024

Status:ongoing

2025

Alien 4.0

The boot of choice for many top athletes, it's a little heavier but has a more natural stride and a thick sole for taking on technical terrain

Buyer’s Guide reviews
In words
Technical specifications

Buyer’s Guide reviews

Performance by context

Ascent

Skiing

Walking

Climbing

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

The charts show our impressions from testing

Product info

Category average

Recommended use

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

Recommended level

Technical Level

Beginner

Intermediate

Advanced

High level

Weight

lightmedianheavy

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

In lab

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

In words

Intro

It's 80–100 g heavier than its closest competitors, but don't be fooled, it vies with the Stratos and DNA Pro for the most podium places in the biggest international competitions. The focus here is on functionality at all costs, even if that means taking on a few extra grams. It's best in class in terms of walkability, and has a BOA dial for the fastest possible closure, as well as a rear anti-snow gaiter. All of which help to shave valuable seconds off your race time.

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

Walking

The toes and muscles of the foot are able to contract and aid the stride, despite the incredibly snug fit, which is more precise than the Alien 1.0. Thanks to the rockered sole, walkability on dry surfaces is excellent. The rocker is easily visible, even to distracted eyes, and makes the Alien faster in transition with better traction on steep, uneven terrain. The cuff rotation is 100% free and the heel is well supported.

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

Lab

It's relatively easy to put on with the liner already in the shell if you tip the cuff completely back. There are three pairs of pads of varying thickness that can be attached to protect the shins, while the foam is wafer thin. The liner is short but has a better consistency than its direct competitors and there are two versions available, one stiffer than the other. If you have bigger-than-average calves the cuff flap may pinch a little, but that's easily resolved by attaching a spoiler.

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

Skiing

This boot is all about stability, aided by the snug heel pocket (be aware of this if you have any lumps or bumps in this area) and the concave shape of the base of the shell. The technical fit is accentuated by the lacing of the liner, especially on the tongue. The BOA dial locks it all firmly in place, and can be instantly adjusted at any moment. On the downhill all this translates into a good overall feel, more forgiving than that of the Stratos VI due to its lower cuff flap, giving it a deeper forward flex.

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

Technical specifications

LINER MATERIALS

carbon fiber

SHELL MATERIALS

carbon fiber

INSERT TYPE

Quick-Step-in

Buckle description

Speed Lock System with Dyneema cable + Boa Fit System

Sole description

Scarpa UFO LT sole in Vibram TOP 85

Liner description

Intuition Race 4.0 SL

No. of buckles

Lean forward

9°/13° - 11°/15°

Available sizes

39-44 EU, no half sizes (boot developed using EU sizing, the mondopoint sizes are approximate for comparison)

Released in

2021

Made in

Italy

Price

1999 €

Declared specsMeasured by us

We measured the measure 27 to get all the details

610 gr

Individual weight

XXXXX

N/A

Liner weight

XXXXX

N/A

Shell weight

XXXXX

N/A

External shell length

XXXXX

N/A

External shell width

XXXXX

N/A

Inner shell width

XXXXX

N/A

Pin distance

XXXXX

N/A

Force to 20° back

XXXXX

N/A

Force to 20° forward

XXXXX

76 °

Cuff ROM

XXXXX

N/A

Maximum cuff height

XXXXX

N/A

Maximum tongue height

XXXXX

N/A

Maximum forefoot width

XXXXX

N/A

Maximum ankle width

XXXXX

N/A

Sole thickness at toe

XXXXX

99 mm

Last

XXXXX

Subscribe to unlock all the Buyer’s Guide reviews Subscribe

Already subscribed?

Top stories

Tutorial

Emergency Repairs on Ski Bases

The Skialper tutorials

Tutorial

Maintenance and complete check-up of ski mountaineering bindings

The Skialper tutorials

2025

Thoughts

At the heart of every ski

Editorial

2025

Intro

Test center

Where the snow is always present

2025

Intro

Skimo skins

It's not all about grip

2025

Instruction

Boot lab: Boots under the microscope

The laboratory analysis of flex, walkability, and thermal insulation of ski mountaineering boots

2025

Intro

Skimo poles

2025

Intro

Safety, a culture of doubt

Beyond the basic definition, there’s nothing as variable as snow conditions and the human psyche when under emotional stress. That's why, after purchasing the right self-rescue kit and airbag backpack, it’s paramount you do your research, train, scrutinize your decisions and, if necessary, opt for plan B. And, at least for now, don’t rely on artificial intelligence.

2025

Race

Light

Tour

Free

Awards

Best bindings 2025

Skiaklper's Awards

2025

Intro

Products for mountaineers

Once you’ve chosen your skis, boots and bindings, your thoughts then turn to harnesses, crampons, ice axe and helmet, though perhaps not everyone, and not straight away. While it’s true that when starting out, especially for those transitioning from resort skiing who just want to start surfing some pow, the important thing is to get self-rescue equipment. It’s equally true, however, that the sport we love is a combination of two words: skiing and mountaineering.

Recommended pairing