Core Pack 35L Road Test

Core Pack 35L Road Test

Nolan Isozaki from took our Core pack all over the world putting it through all the tests he could think of.  See why this pack stands out!

Road Test

Being on the road (or in the sky) searching for the gnarliest peaks or driest snow is a constant for me. When I was offered a chance to test the RMU Core Pack 35 L, I jumped on the opportunity to hang out with this quiver killer, marketed as a travel pack for anywhere from Indian Creek to Chamonix. To test the pack, I brought it with me from Alaska to Los Angeles, Madrid, San Sebastian, Tokyo, and finally, Niseko, the powder capital of the world. I’ve dragged it through my fair share of airports and was able to strap the skis onto the Core for some early season skiing, taking into consideration that this is not a specific backcountry pack, but rather, a dual-purpose pack. 


The Core is a sleek pack with looks that feel as much at home in urban climes as they do out in the elements. The pack was the center of many compliments while in transit on the long way to Hokkaido. The Maroon of my pack changes hues depending on lighting and can appear anywhere from dark red to deep maroon (there are five color options at the time of writing). The first thing people comment on are the burly buckles and remarks on how tough the pack looks. Design language of the RMU Core straddles the worlds of urban sensibility and an outdoor pack. The wooden ski core spine attracts the brunt of the attention when exposed, along the lines of: “Is that really wood?"


This is one burly gear hauler, with a tough polyurethane laminate on top of the nylon base. I never had to worry about babying the pack. One look at the specs sheet will tell you this bag is tough as nails, which inspires confidence in most scenarios I dragged it through.


Steel buckles follow well with the design philosophy of the rest of the pack, over-engineered with the right amount of gusto. RMU have forgone plastic buckles commonly used in ski packs and have opted for oversized steel tabs, which are perfect when I can feel my hands but can be clumsy with thick gloves or frozen digits. The satisfying “click” that accompanies buckles is replaced with visually IDing that the tabs were indeed in place.


The RMU features a tough water-resistant 630D nylon and polyurethane coating for the exterior and a 1280D ballistic nylon bottom with hypalon reinforcements. The interior sports a “wet section” for avalanche tools and skins or anything you would want to keep out of the main pack.

Who It Suits

For those who want a bag built like a tank to do it all. If you can only rock one bag for a wide variety of conditions (like while traveling), the RMU Core can take you from the airport to slopes and to hikes if you are willing to compromise on its heavyweight pedigree. It’s sort of like taking a dive watch to the office; most of the time, it’ll feel over-engineered. The RMU Core is a perfect travel companion, just a tad bit heavy for hiking, but just right for lift access skiing and trips to the side and backcountry. It ticks all the boxes it sets out to tick with broad strokes.

Who It Doesn’t

Weight weenies or those into more technical pursuits in the spirit of light and fast. This pack is a heavyweight both in carry resolution and weight. Running and scrambling with the pack can feel restricting. The pack does not move with the body as well as other dedicated packs because it is quite stiff without as much hip to shoulder articulation.

Rocky Mountain Underground have really considered the details that make a good all mountain pack. The Core’s organizational features in both the main and front compartments almost pack the bag for you. With top loaders, you often have to be conscious of layering your gear in a way that prioritizes heavy-use items on the top or heavier items mid-pack. With the Core’s many internal pockets and a zipper that snakes along the whole side of the pack, granting complete access to everything, it is hard to poorly pack the bag. These features work seamlessly for gear-heavy outdoor pursuits and are the perfect companions for the daily commute or trip around the world, with plenty of options to store cables, hard drives, batteries, keys, gloves, avalanche gear, etc. If the outside of the Core is about understated good looks, the liner is a loud orange, matching the buckles adorning the side of the pack. The bright interior (150D Poly) means no more looking for that one black charger cable in the black depths of a bag.
The main compartment swallows two jackets easily and features pockets to organize electronics and cables. They are sectioned off with black elastic bands, which do a good job of keeping things where you put them, even with the rough and tumble that can occur during travel.
 The organizational aids continue onto the front compartment, which features daisy chain loops (I strapped my watches into it but I could see them being used for keys, a mini Dopp kit, or anything that needs easy access) and a sleeve that fits anything from magazines to notebooks. On the flip side, they are also perfect for an avalanche probe and shovel.
The top flap of the bag features a goggle/sunglasses compartment. I stowed my sunglasses and lens cloths while in transit, swapping them for goggles when it came time to ride. The interior is lined with a soft, lens cloth-esque material that I trust with my goggles (for the downhill) and sunglasses (for the uphill). This is another feature that showcases how versatile the Core is for everything from airport to alpine and how carefully considered features specific to skiing are.
The Core ships with a matching laptop sleeve that hooks onto the inside of the main compartment to avoid sagging. One niggle is that I wish the interior fabric of the sleeve was less grippy, as my laptop case's rubber feet would stick to the sides, forcing me to jostle the laptop around until it found its way in. If your laptop runs without a case though, this is not a feature I would worry about. Easy laptop access also streamlines going through airport security or swapping the laptop for ski gear. This reiterates the Core’s versatility as a daily driver you can take for some pow slashing.

Straps and workflow

There is a break-in time for the straps, padded with a thick foam, which were pretty stiff for the first few weeks. In conjunction with a contoured back panel featuring a large central vent, weight is distributed quite well once you find the sweet spot. RMU added micro adjustment options on how high or low you want the bag to ride. Because the top of the Core is level with the top of the straps, it stays out of the way of a helmet, allowing you to swivel your head without running into the top of the pack. This also keeps you from riding top heavy in case you want to keep a camera or water bottle at the top of the pack.

Although the RMU Core has a sweet spot when static, introducing dynamic movements tosses up the equation. The Core rides quite stiff and when twisting and rotating the upper body in the opposite direction of the lower body, like the torquing seen in downhill skiing. The upside of the stiffness is that the back panel and strap work in conjunction to distribute weight very well, even with A-frame style ski carry and boots in tow.

The narrow sternum strap seems out of place on this pack. If the rest of the pack is all about oversized buckles, beefy straps, and carry handles, the sternum strap seems to be an afterthought. The “W” shaped buckle can be a bit small and slippery without gloves. The strap works very well, but I feel that slightly beefier hardware would have been a better match here.

Each strap on the RMU Core has an elastic retainer loop, keeping the excess length in check. This small feature makes a world of difference when traveling. With minimal loops to snag compared to other packs, I was very confident with stashing this under airplane seats, in the overhead compartments, and into the trunks of cars. A drawback is that I appreciate having easy access to straps when grabbing with large gloves or hands that have lost their feeling. There isn’t an option to let the flaps fly should you want (save snipping off the orange retainer bands), but if you have better control of your hands in the cold than I do, this shouldn’t be a problem.

A small but exceedingly useful feature that sets the RMU Core apart from other travel carry (as far as I know) is its handle on the bottom of the pack. In the trunk of a car piloted by an enthusiastic driver, a pack can often end up upside down. Although not a feature to write home about, the handle on the bottom expedites the process from trunk to adventure, something we can all appreciate.


Space and Access

This is a tall pack rather than a stout pack. As a result, the Core carries well and keeps its center of gravity close to the body, ideal for sports that rely on gravity sense, such as skiing. Minimal depth also means you’ll stay on the lift and won’t be hanging on by the seat of your pants. Because the pack is tall and the zippers on both the avalanche and main compartment zip to the bottom of the pack, access to items stashed at the bottom has never been an issue (except when in A-frame carry). These dimensions also mean it is the perfect size to stash into an underseat compartment (for short flights, because legroom trumps convenience for longer stints).

Adventure Setup:

The RMU Core is the perfect size for all day inbounds or on a day tour, with enough room for a few layers, avalanche gear, a snack, and perhaps camera gear. Its water-resistant exterior means that for things like Hokkaido powder skiing and even a bit of rain, your gear should be well protected from the elements. The pack does wet out under heavy precipitation, dampening the interior, but does not soak through (more on that later). This is my typical Hokkaido setup, which I managed to quickly snap a photo of before it drowned under the bottomless powder keg.

Day-to-Day Setup:

35 liters is the perfect size for a day-to-day carry option. In Southern California, where I tested this bag in fair weather, it could even be considered a bit large. In Hokkaido, the 35 liters is perfect for daily pursuits. I add a puffy jacket and an emergency hardshell because precipitation and drastic temperature changes from day to night is a way of life. In an urban setting the avalanche gear section was perfect for dirty clothes or wet beach clothes that I wanted to isolate from the rest of the pack.


The pack distributes weight well with its two large panels, separated by a central vent featuring a wooden ski stay. This pack’s main downside is that it tends to run very hot compared to more technical packs when performing aerobic activities in warmer temperatures. The RMU Core excelled as a travel and a ski pack, but struggled in fair weather pursuits due to heat buildup.
RMU has coated the outside of the pack with a PU (polyurethane) coating that has survived almost everything I’ve thrown at it, except the security checkpoint at Juneau’s airport in Alaska. Something in the conveyor belt probably snagged against the pack, taking off a bit of PU laminate with it. Although it has a PU coating, it struggles a bit with keeping dry. With snow buildup on the surface of the pack, going indoors meant that water was able to accumulate on the bag and transfer some moisture into the goggle compartment. Not a big issue, but must be considered (for example, don’t put your phone in the goggle compartment on a wet day).

The Good

  • Good access to gear throughout the bag
  • Burly build and good organization
  • Versatile design for travel and outdoor activities
  • Top of the bag is low enough to not hit your helmet or restrict head movement
  • Can feel rigid, but the stiffness helps with distributing heavy loads

Not So Good

  • Helmet sling is tight-fitting
  • Buckle tabs require visually checking they are secure; no auditory click for confirmation
  • Moisture may get into the goggle compartment on wet days with snow buildup on the pack
  • Can feel hot in warmer weather activities


It is very clear that this pack was designed by skiers for skiers. Rocky Mountain Underground’s first pack is a winner both in concept and execution. It promises to be a travel pack with the chops to shred it up on a pow day, and delivers on these fronts with flying colors. I would recommend the Core as a “one pack quiver” for both a ski backpack and a carry-on if you will be primarily riding lift access runs with occasional sidecountry or backcountry ventures. RMU’s design has kept the center of gravity close to the body for that crucial gravity awareness during descents. The Core will have a break-in period and can sometimes feel quite rigid, but its stiffness will be perfectly suited for dispersing heavy loads for trips to cruising altitude and back.

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