- Split leather upper with Friction Skin
- Lateral Torsion System
- Elastic gore with hook-and-loop strap
- Anti-deformation midsole
- Zenith rubber sole
- 4.0 – 4.5 mm thick outsole (depending on size)
Size Tested: 13
Days Tested: 15
Test Locations: Eldorado Canyon, Clear Creek Canyon, Shelf Road, & South Platte, CO; Ten Sleep & Wild Iris, WY.
Boreal calls the Mutant a “high-performance shoe which excels at bouldering or sport climbing.” They also say about the Mutant, “To climb the hardest routes and boulders, a shoe must excel in all areas; to find friction wherever it appears. Edges, smears, heel and toe hooks; any of these may be needed to ensure a successful ascent. With the Boreal Mutant, there is no compromise.”
We’ve said before that no shoe can truly excel in all areas, so the purpose of this review is to get clearer on where the Mutant really does shine, how it stacks up against a couple of its direct competitors, and what sort of climbers would be best suited for the Mutant.
Construction, Fit, and Comparisons
At a quick glance, the Boreal Mutant looks like a mix of two very good shoes, the Five Ten Hiangle and the La Sportiva Miura Lace (reviews coming soon). Like the Hiangle, the Mutant is downturned but not overly asymmetric, with a generous helping of sticky rubber on the upper, and a single velcro strap near the opening that serves as the closure system. But the Mutant’s toe box is more reminiscent of the Miura Lace, since it has more taper near the end compared to the Hiangle. The result of all this is a shoe that climbs like a hybrid of both the Hiangle and Miura Lace, which makes it a compelling option that hasn’t gotten the attention it deserves.
When reviewing the Mutant, I was drawn to the Miura Lace and Hiangle comparisons because all three shoes, while distinct from one another, are high-end sport climbing shoes that feature both a softer mid-sole and toe box. This is in contrast to shoes with either more downturn or a stiffening plate underneath the toes (such as La Sportiva’s P3 system used in the Solution). As a result, the Mutant, Miura Lace, and Hiangle all cater to a similar genre of climbing: complex face climbing that typically involves a combination of pockets, edges, and smears. While the Mutant shares a few key features with its competitors, analyzing how the shoe differs from them offers the most insight as to where it best performs.
Compared to the Hiangle, the Mutant has a slightly softer feel, in part because of the toebox shape I mentioned earlier. The front of the Hiangle ends abruptly with a much more blunt toe cap than the Mutant, whose toe box tapers to more of a point. This reduces the Mutant’s power along its inside edge for thin edging compared to the Hiangle, but simultaneously boosts its ability to get purchase in pockets, corners, and the like.
This is where the comparison to the Miura Lace comes in. The Miura Lace has a similarly tapered toe and, with their softer toe boxes, both the Miura Lace and Mutant share a similar aptitude for both pockets and edging. While they are very similar in this important aspect, the Mutant is more asymmetric and downturned than the Miura Lace, which gives the Mutant a slightly more aggressive feel. The Mutant is also higher-volume and broader underfoot than the Miura Lace, which will likely affect the fit depending on how wide your feet are.
Just like the Hiangle and SCARPA Instinct VS, the Mutant has the charming quality of being difficult to get on and off initially. This is partially due to the snug fit of the shoe (which is generally a good thing for climbing performance) but the tradeoff is more difficulty getting in and out of the shoe. The proximity of the single velcro strap to the opening of the shoe also bears some blame. However, the strap placement does help in one area: the higher placement does a better job of staying out of your way while climbing. This is true in general, but it’s especially true when toe hooking. Having the shoes be a little harder to get in and out of is the price paid for a discrete closure system and snug fit. I don’t consider this to be a deal-breaker for either the Mutant or the Hiangle since both shoes climb so well, but it is something to consider.
As for sizing and stretch, I went with my street shoe size and thought the fit was exactly where I wanted it to be. Despite the softer materials on the upper, the Mutant didn’t stretch as much as I thought it might. It did end up stretching about a half size, but not enough for me to wish that I had sized down. However, if you’re between sizes, I’d recommend rounding down for the Mutant.
The upper on the Mutant consists of split leather that’s connected by a slightly elastic piece of green fabric, all joined in the middle by a softer, stretchy fabric tongue that sits under the velcro closure. As you move towards the toe box, the leather upper gives way to what Boreal calls “Friction Skin.” This material caps the toe box and supplements the regular rubber above the big toe. Friction Skin basically consists of small pieces of rubber “painted” onto the upper using an adhesive. Because it’s a rubber/glue hybrid, it definitely feels different than rubber alone (and sacrifices some friction in the process) but it compensates by allowing the toe box to conform to your foot much better than a regular slab of sticky rubber.
Compared to the traditional, full-rubber toebox of the Five Ten Hiangle, the Friction Skin on the Mutant allows for much more conformal fitting. This is another area where the Mutant falls on the soft-and-sensitive side of performance relative to many of its peers.
Sensitivity and Performance
For on-rock performance, I came to think of the Mutant as my go-to shoe for the bizarre, crack/face climbing of Eldorado canyon, where a single pitch often combines intricate sequences of holds and stances ranging from sharp edges and dimples, to smearing in corners or dihedrals. The sensitivity of the Mutant allows you to assess each hold and get the most out of each stance. All of this is less important if you’re climbing up crisp edges all day, where you might want something stiffer in both the toe box and mid-sole to decrease foot fatigue.
The Boreal Mutant is a soft, sensitive, face-climbing shoe that blends the edging power of the Five Ten Hiangle with the greater versatility and precision of the Sportiva Miura Lace. It is slightly higher-volume than both of those options, so the Mutant performs well while maintaining an extremely comfortable fit.
The Mutant isn’t the most aggressive shoe on the market in terms of either downturn or asymmetry, and the lack of reinforcement under the toe box shows a clear emphasis on sensitivity over supreme edging power.
So if you are looking for a shoe for steep limestone or endless granite credit-card edges, you’ll find options that cater more directly to those specialties. But anyone looking for a shoe that performs across a diverse set of climbing styles will be very, very well served by the Mutant.