by boris d (used product regularly)
Just wanted to add a few observations regarding the fit of these boots. Enough was said about ski performance and I'm not a ski expert to add much on this subject.
It was an emotion-driven purchase. My beloved LS Syborgs all of a sudden turned into torture device when some kind of bony protrusion grew on my foot and it gotten really painful after only a few hours of touring, especially when in a ski mode. I went to the ski shop to try to do something about, saw Alien RS, put them on and pulled out my cc!

It's been a little tight at the forefoot first few outings but then it went away and now the boots are really comfy! I had the liners molded but frankly I think the fit improved just from usage. Anyway: my feet are old, medium width, pretty wide at the toes but these boots fit great! I probably went with 1/2 to 1 size too large so the fit is not "performance fit" but they ski great for me and very comfortable. No hot spots, no blisters, nothing! Maybe I should try a foot-bed to take up some of the slop but maybe it's like trying to fix what's not broken?

A few other things: crampon fit with my crampons that I assembled for Syborgs from several different parts is awesome! BOA adjustment is fantastic, super easy to tighten and you just pull the knob and it loosens. The gaitors have no zippers to break. Liners seem thicker and way warmer compared to Syborgs. It's really easy to put the boots on which is kind of nice when you are on a multi-day tour! I'm in love with these boots but let me point to a few negatives:

Ski/walk mechanism is way harder to work compared to Syborgs. You need to bend back to reach the lever and it may take a little fiddling. Really no big deal and I'll probably learn to do it quicker with time.

As others pointed out, the cord for tightening gets frayed pretty early and the cord slips through the locking fitting when tightened hard. A knot on a cord would probably solve the slippage problem.

I'll add other negatives if I could think of anything else.
Comment on this review:

by Anthony O (downright abused product)
Pros: Light-very stiff for weight. walk range is great, similar to other race style boots. Boa is great for easy adjustments. Love the simplistic single throw for switching to ski mode. Tread is very durable. I have only skied race style boots, I've never skied an alpine boot, but comparatively this is the stiffest boot i've used. I have no problem on 100mm waist skis with this. Wouldnt hesitate to use on 105s, but I am a balance skier, I dont drive from the cuff.

Cons: Durability of gaiter pulls-ripped off pretty early while sliding a liner in. Cord that also serves to put the boot in ski mode also visibly is frayed after about 50 days and also slips through the cam lock. Like others I have just tied a knot so that it will not slip through. I have also found the single throw latch to loosen over time, requiring occasional tightening. I am also concerned about the stress on the small cam lock from the added knot, though I havent noticed any issues yet. I also do not like that the sole is very flat. Comparatively to some other brands, there is almost no rocker, so even though ankle ROM is huge, the "naturalness" of the walk is impeded by the flatness of the sole (though that may be preference). I also question the use of the carbon infused grilamid throughout the entire shell, I will explain in the fit notes.

Fit notes: very narrow toe, not anatomical shape. symmetrical rounded pointy ish toe (never seen anyone who has feet or toes that look like the toe box on this) Fairly low volume. My foot measures a 27 but I have to do a 28 in this and its still too tight for my width. The heel and midfoot are wider. I personally have a wide forefoot and narrow heel. This boot is too tight in the toes and too sloppy in the heels for me. I had to add a lot of foam in order to get good heel hold on this, I also had to add a foam shim to the shin area to held with heel hold. Because of the very specific fit of the boot, it is even more limited because of the carbon fiber infused grilamid. This material is stiff, but is extremely difficult to punch. And Scarpa doesnt approve of punching it (voids warranty I believe). I have had mine punched but compared to normal grilamid I was much more limited in how much I could punch it. So if your normal practice is to downsize shell and punch it out, or have a suboptimal fit and modify it, the potential for modification is very small. Even after punching I didnt have enough space in the big toe area so I used a razor to cut out a couple mm from the inside of the liner by my big toe. This boot should work for you if you have a narrow forefoot and in general low volume feet. Talk to the guys on this site, they will steer you in the right direction as far as fit. If you have average, wider "american" feet, my guess is these will be a tough fit out of the box and may not work.

Notes to Scarpa: You know what most people's feet look like, as evidenced by the Maestrale, and other mountain boots, like the Mt. Blanc or the new Ribelle or various other boots. Why do you change the last for "race" boots? Not all people who like to race suddenly morph the shape of their feet. Also, if you are going to make a very specific type of fit that doesnt work for a lot of people, at least make the lower part of the shell out of an easily modifiable material like normal grilamid so that those of us that dont have small elvish pointy toes can have a solution for fit.

Ultimately I will keep the boot, unless someone wants it, but I cannot bare it for multi-day or very heavy mileage days. But if I want high performance skiing or dont plan on a super long day I may take them, but usually comfort wins out for me, so these may be collecting dust for me now. Still an excellent option if it fits you, definitely try in store before purchase.
Comment on this review:

Question from Bruce A
Is there a cuff cant on this boot? Thinking no, but somewhere I thought I read a review that mentioned a cuff cant.
Answer from Trace Leches
Hey Bruce! Nope, no cant cuff! They went light and burly with this one!
Answer this question:

by Pete (used product regularly)
Got these at the beginning of the season and have pushed them hard, what an amazing upgrade from my old TLT 5 Ps. Scarpa seems to advertise this as a race boot, but I don't think this is the case, not quite light enough, the ankle articulation isn't quite there, and there is much too much resistance pushing the boot through the articulation for it to be called a true race boot. I think skimo.co makes a good distinction by calling this category "race-plus." Boy for the weight does this boot ski, easily equal to my old TLTs, in my opinion everyone between freeride shredders and racers should be zipping around on these.

Sizing is tighter and narrower than most Scarpa boots, I'm commonly a 27-27.5, I chose a 27 in these, they fit quite nicely but it's definitely a performance fit.

Gaiter is amzingly thought out, and I love that they added a clip for binding tethers. My only complaint is that the cam device used to adjust tightness of the upper eats at the dyneema cable, hasn't failed yet, but is visually core shot. A thought as to how Scarpa could make these better is by using a full carbon upper, retaining the carbon grilamid lower and lining it with weave as in the current 1.0, this would make the boot considerably stiffer and lighter without compromising durability of the lower for scrambling. Perhaps the new 1.0 will fill the ticket.
Comment on this review:

by Mark E (used product regularly)
These Alien RS boots ski astonishingly well for as light as they are. The innovative Boa and upper cuff tightening systems provide for something that feels a bit like a four buckle design in a 2 lb boot. I have fifty days or so of skiing in these boots, and a couple days of ice climbing. No concerns or complaints about durability. Scarpa suggests that these boots are best for skis 85mm or less. I ski these on 84mm skis, but feel that they could comfortably power a bigger ski. A ski partner skis these boots on 95mm skis without complaints.

The boots are a little tight in the toe box, and fit a little bit short. I usually ski a 26.5 ("performance fit") boot, and my size 27 Alien RSs are barely big enough (I have a footbed in the boots to raise my arch and shorten my foot a bit).

Not an ideal boot for ice climbing. The offset toe welt does make the boot natural to walk in and tour in, but might require you to bend your crampons' toe bails to get a snug fit. The ski/walk mode arm interferes with the heel clip on most crampons, meaning you'll need to loosen your crampons to switch between walk/ski mode.

The boots are comfortable and dexterous enough that I have no difficulty driving my manual-transmission Subaru in the boots, and often find myself running errands in town on my way to/from skiing in the boots.

This is a perfect boot for ski mountaineering and any sort of long distance touring. If your objective is moving quickly and confidently on snow in the backcountry, I'd suggest that the Alien RS is a perfect boot.
Comment on this review:

Question from Peter D
Hi there. Was wondering if the Aliens RS can be punched. Of course Scarpa states against that and it would devoid the warranty. Currently skiing 27.5 Dynafit Beast with a small punch for my right foot bunion. Tried the Aliens RS in 28 and got a really good fit except a pressure point in the bunion. It might go with liner molding, but it did not in case of the Dynafits. I would probably need couple of millimeters punched, do you think its doable?
Thanx for advice Peter.
Answer from eric
Peter- Yes the punch would void any warranty on this boot. That said, there is some capability depending on where on the boot it needs to be modified.
Answer this question:

Question from Jeff
I wear a 27.0 in the new Maestrale RS 2.0. What size would that be in the Alien RS?
Answer from jbo
Hi Jeff, SCARPA uses similar lengths across their line of boots, but the widths can vary. The Alien is noticeably narrower than the Maestrale in the same size, but about the same length.
Answer this question:

Question from James O
Has anyone managed to get shorter leashes (like the Dynafit Guide) to work with this boot? I can't find any suitable locations to clip into. I realize the around-the-cuff long B&D brand ones are an option, but I'd like to use something shorter if possible.
Answer from Trace Leches
Hey James! Yeah, totally! I actually use the exact combo you're mentioning. There's a small d-ring riveted into the upper shell that you can girth hitch the steel ring from the Dynafit Guide leash into!
Answer this question:

Question from Erik
Can't quite get used to the 13° max forward lean on these boots. Looking at the clamp in the back for adjusting the forward lean, it looks possible to modify this to get a couple of more degrees in (drilling to offset the holes).
Any ideas if this mod has been done before?
And is it just me, or is the forward lean accually not quite normal on these boots?

Best regards!
Answer from Trace Leches
Hey Erik! Not sure if it's actually been done before but I've had this talk multiple times, including with myself. The forward lean isn't quite where I want it to be either. A less permanent (and potentially warranty voiding) solution would be to put some foam on the back of the cuff of the liner to just bump your lower leg a bit further forward. We've done that many times on these boots before to account for tiny calves or not enough forward lean.
Answer this question:

Question from Trevor J
Thanks for the boots. very well made and impressive in many ways :) what crampons work well with these? any crampon limitations with these boots that you've noticed?
Answer from Trace Leches
Hey Trevor! The Petzl and Camp crampons seem to work really well with the boot, but that's only if you don't plan on putting the boot into ski mode while front-pointing. If you plan on keeping the boot locked and front-pointing, use something like the Grivel SkiMatic 2.0 crampon that levers on via the toe.
Answer from Drew P
Camp XLC390 and BD Neve don't fit this boot at all, but the Grivel Skimatic fits it great!
Answer this question: