Last tested
2024
Status:ongoing
2025

Alien 4.0

Pro's choice Race
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?
Log in
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?
Log in
Recommended level
Technical Level
Beginner
Intermediate
Advanced
High level
Weight
lightmedianheavy
Subscribe to unlock all the Buyer’s Guide reviews Subscribe
Already subscribed?
Log in
In lab
Subscribe to unlock all the Buyer’s Guide reviews Subscribe
Already subscribed?
Log in

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?
Log in
product
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?
Log in
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?
Log in
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?
Log in

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
2
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?
Log in
Top stories
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.

2025
Split All Mountain
Intro
Boards, boots, and bindings for splitboarding

Materials are evolving, which is increasing the opportunities for pushing the boundaries of mountaineering splitboarding. It’s no longer just about easy tours, a few jumps and a beer. Thanks to innovative new setups and growing knowledge within the community, long ascents and steep terrain no longer intimidate.

2025
Intro
Skimo bindings

They’re probably the element of your setup that’s evolved the most and seen the most crossover between disciplines. Which is why in general lighter bindings have adapted to make allowances for the trend for opting for wider skis, with hybrid drilling patterns and a greater selection of ski brakes. But the aspect that requires most scrutiny is the height difference between the front and rear pins.

Recommended pairing
tested 2025
Skis
Race
Dynafit
DNA Pro
Width Center: 64 mm
Weight: 690 g
Top match
tested 2024
Skis
Race
Atomic
Backland 62 UL Vert
Width Center: 62 mm
Weight: 650 g
Top match
tested 2025
Skis
Race
Dynastar
M-Pierra Menta
Width Center: 65 mm
Weight: 700 g
Top match
tested 2025
Skis
Race
Ski Trab
Gara World Cup 60
Width Center: 64 mm
Weight: 700 g
Top match
tested 2025
Skis
Race
Ski Trab
Gara World Cup 70
Width Center: 64 mm
Weight: 710 g
Top match
tested 2024
Skis
Race
Fischer
Transalp RC Carbon
Width Center: 65 mm
Weight: 690 g
preview 2025
Skis
Race
Made for women
Ski Trab
Gara World Cup 60 Lady
Width Center: 64 mm
Weight: 685 g
preview 2025
Skis
Race
Made for women
Movement
Race Pro 66W
Width Center: 66 mm
Weight: 620 g
tested 2025
Skis
Race
Hagan
Ultra 65
Width Center: 65 mm
Weight: 700 g
preview 2025
Skis
Race
Kästle
TX 65 WC
Width Center: 65 mm
Weight: 690 g
tested 2025
Skis
Race
Movement
Race Pro 66
Width Center: 66 mm
Weight: 675 g
PEOPLE'S CHOICE RACE
tested 2025
Skis
Race
Dynafit
Mezzalama
Width Center: 64 mm
Weight: 790 g
tested 2025
Skis
Race
Elan
Lynx 65 UL
Width Center: 65 mm
Weight: 690 g
SMART CHOICE RACE
tested 2025
Skis
Race
Ski Trab
Gara
Width Center: 64 mm
Weight: 760 g
tested 2025
Skis
Race
Atomic
Backland 65 UL
Width Center: 65 mm
Weight: 670 g
Recommended setup
tested 2025
Bindings
Race
ATK Bindings
Revolution Brake World Cup
Type: full pin
Weight: 122 g
Top match
preview 2024
Bindings
Race
ATK Bindings
SL Brake World Cup
Type: full pin
Weight: 135 g
Top match
tested 2025
Bindings
Race
Dynafit
DNA+
Type: full pin
Weight: 128 g
Top match
tested 2025
Bindings
Race
Ski Trab
Titan Gara WC + Stopper
Type: full pin
Weight: 160 g
Top match
preview 2025
Bindings
Race
Grizzly
GR 98 II
Type: full pin
Weight: 98 g
Top match
preview 2025
Bindings
Race
ATK Bindings
Trofeo Brake
Type: full pin
Weight: 145 g
preview 2025
Bindings
Race
Light
Kreuzspitze
RS
Type: full pin
Weight: 169 g
preview 2025
Bindings
Race
ATK Bindings
Revolution World Cup
Type: full pin
Weight: 105 g
tested 2025
Bindings
Race
Plum
R World Cup
Type: full pin
Weight: 144 g
tested 2024
Bindings
Race
Grizzly
GR 48
Type: full pin
Weight: 48 g
Similar products
tested 2025
Boots
Race
Made for women
Scarpa
Alien 1.0 WMN
Buckles: 2
Weight: 735 g
tested 2025
Boots
Race
Scarpa
Alien 1.0
Buckles: 2
Weight: 785 g
SMART CHOICE RACE
tested 2025
Boots
Race
La Sportiva
Stratos Hybrid
Buckles: 2
Weight: 728 g
PEOPLE'S CHOICE RACE
tested 2025
Boots
Race
Dynafit
DNA
Buckles: 2
Weight: 810 g
BOOT OF THE YEAR RACE
tested 2025
Boots
Race
La Sportiva
Stratos VI
Buckles: 2
Weight: 530 g
tested 2025
Boots
Race
Dynafit
DNA by Pierre Gignoux
Buckles: 2
Weight: 510 g
tested 2024
Boots
Race
Dynafit
Mezzalama
Buckles: 2
Weight: 875 g
tested 2024
Boots
Race
La Sportiva
Raceborg II
Buckles: 2
Weight: 735 g