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Rab began making sleeping bags in 1981, drawing on their experience as mountaineers, and they remain known as "Masters of Insulation" today, proud to be second to none in making truly practical sleeping bags for the field. As proof of this, the Mythic Ultra series, released in 2020, is still one of the lightest full-mummy-style down sleeping bags in terms of weight-to-insulation ratio, and its outstanding technical capabilities and originality are beyond doubt.
Rab's lightest sleeping bag series, the Mythic Ultra has been expanded with the release of the amazing Rab Mythic Ultra 120 Modular, Rab Ultrasphere 4.5 mountain hike in April, and we'd like to share our impressions with you.
table of contents
- Main features of the Rab Mythic Ultra 120 Modular
- Detailed review
- Design and weight: A comfortable, lightweight, and compact design that eliminates unnecessary elements to the maximum extent possible without sacrificing comfort
- Insulation: Lightweight yet warm thanks to premium goose down and TILT technology that minimizes heat loss
- Combine it with the simultaneously released "Ultrasphere 4.5 Sleeping Pad" to create a lightweight and compact sleeping system weighing under 700g
- Summary: The careful design that minimizes weight while maintaining minimum comfort may be the optimal solution for modern minimalists
Main features of the Rab Mythic Ultra 120 Modular
The Rab Mythic Ultra 120 Modular is a down sleeping bag that, when paired with a sleeping pad, minimizes weight and allows for comfortable sleep in low-temperature environments. The rear sleeve allows the sleeping bag to be secured to the mattress, eliminating the back and head sections, preventing cold spots while significantly reducing weight. The bag's fill is made of extremely high-quality 900FP European goose down (water-repellent finish), and the bag's top and under-leg sections feature Rab's proprietary heat-reflective TILT (Thermo-Ionic Lining Technology) for top-of-the-line insulation. When paired with Rab's Ultrasphere 4.5 weighs just 700g in total, yet remains resistant to temperatures as low as 0°C (measured according to Rab's proprietary standards). Packing uncompromising functionality and comfort into a minimalist size, the Mythic Ultra 120 Modular is ideal for a wide range of light and fast adventures, including multi-day hikes, fastpacking, alpine climbing, river climbing, and bikepacking.
Favorite points
- Incredibly lightweight and compact
- High thermal insulation that can withstand temperatures down to 0°C when combined with a mat with an R value of 4 or higher
- Wide enough to not feel cramped
- Mattress sleeve on the back prevents slippage even when you roll over
- Pillow sleeve for storing folded clothing etc
Interesting points
- The short, small zipper is prone to getting caught, making it difficult to get in and out (although it is angled to make it easier to get in and out)
- Difficult to ventilate when it's hot and stuffy
- High price for the temperature range
Main Specifications and ratings
| Item name | Rab Mythic Ultra 120 Modular |
|---|---|
| Adapted height | 185cm |
| Storage size | 16 × 32cm |
| Fabric material |
|
| Insulation material | 900FP European Goose Down, Nikwax and Fluorocarbon-Free, Water-Repellent (120g) |
| Official weight | 330g |
| Official lower temperature | 0℃ *Based on Rab's own sleep limit temperature standard |
| accessories |
|
| evaluation | |
| Comfort | ★★★★★ |
| Thermal insulation | ★★★★☆ |
| weight | ★★★★★ |
| Storageability | ★★★★☆ |
| Easy to use | ★★★☆☆ |
| Durability | ★★★☆☆ |
Detailed review
Design and weight: A comfortable, lightweight, and compact design that eliminates unnecessary elements to the maximum extent possible without sacrificing comfort
At first glance, the Mythic Ultra 120 looks like a regular mummy sleeping bag, but it has some drastic reductions in the details
Let's start by looking at the unique design of this sleeping bag. At first glance, it looks like a typical "mummy style" sleeping bag used for mountaineering, but in fact, it has a structure that differs from a mummy style in some small details
Incidentally, mummy-style sleeping bags were once recognized as a more streamlined form compared to regular futons (square, also known as envelope-style), but in recent years, mattresses, which act as futons, have rapidly evolved to become lighter and more insulating, so even the mummy-style sleeping bags still have room for improvement in some ways, and some ultralight hikers have sought to make them lighter in various ways. This process has led to the development of sheet-like "quilt-style" sleeping bags and "half-size" sleeping bags that only reach from the feet to the stomach
the Mythic Ultra 120 Modular is largely in line with this, and the concept of this sleeping bag is to make the entire sleeping system lighter and more compact by eliminating as much of the parts that can be left to the mattress as possible. While maintaining the basic mummy-like shape, the padding in the back area, where the loft would be crushed by the weight of the body, has been omitted, and the hood above the shoulders has also been omitted, creating what could be called a "pseudo-mummy" structure.
Since it is intended to be used in conjunction with a sleeping pad, the back of the sleeping bag does not contain any padding
The sleeves are excellent for securing the sleeping bag to the mattress and preventing cold spots
At this time, the sleeping bag itself is fixed by the mattress sleeve and pillow sleeve, so it will not shift up or down or side to side. In other words, even if you roll over, the thin part of the back will not turn to the side (up), so you don't have to worry about the cold air hitting you
It comes with a sleeve that connects and secures the sleeping bag and mattress so that the mattress always rests on the back
Also, as you will find out when you actually sleep on it, no matter how much you move your body while sleeping, the sleeping bag stays firmly fixed on the mat and does not move, so your body will not stick out from the mat, making for an incredibly comfortable sleep
I've actually already experienced a similar system in the FREELIGHT Wrapta3.5 sleeping bag made by FREELIGHT, a Japanese UL manufacturer, and it's been a secret favorite of mine ever since. This system of "securing the mattress and sleeping bag with sleeves" is so comfortable that I want to give it a big shout-out
Although the padding in the back area has been omitted, unlike the ``quilted type'' where the entire back is omitted, the Mythic Ultra 120 Modular has padding also packed into the back of the lower body area, so even if space is created by bending your legs, it does not get too stuffy, and it is also comfortable to be able to move your lower body somewhat freely.
The only part that is padded is the back, with the lower body padded 360 degrees, making it gentle on side sleepers
Wide, comfortable shape that allows for easy movement inside the sleeping bag
In the past, I've had the disappointing experience of buying a sleeping bag that was extremely narrow in width in an effort to cut weight to the bare minimum, making it extremely cramped. Because of this, I always try not to trust the value of sleeping bags that advertise their lightness until I've actually slept in them, but as soon as I got into this sleeping bag, I was immediately relieved by its exquisitely refined comfort. The high-quality, warm down doesn't feel heavy, doesn't restrict movement, and yet gently envelops me without leaving too much space
Pillow sleeves are convenient because you can stuff your clothes into them to make a pillow
The head is completely omitted, but the sleeve is bag-shaped, and excess clothing can be placed inside it to use as a pillow
The fixed sleeve on the head is bag-shaped (see photo above), and you can stuff spare clothes, towels, etc. into it to use as a pillow. While it's certainly comfortable to have a pillow, it's a very useful feature since you might be hesitant to bring one just because it adds to your luggage
I put my winter clothes in the head sleeve and it made a perfect pillow
The stripped-down zipper makes it lighter, but it's a bit difficult to use
The structure has been thoroughly designed to eliminate all unnecessary elements, even in small parts such as zippers, and the jacket has an extremely short design that only opens up to the chest
The zipper at the entrance has been shortened as much as possible to reduce weight, and is angled to make it easier to get in and out
According to the manufacturer, "We chose a diagonal zipper to ensure easy entry and exit and sufficient ventilation even on summer nights," but while a diagonal zipper does indeed provide a wider opening than a vertical zipper, it still has its limitations and can feel a bit cramped when getting in and out. The zipper parts are also small, making them difficult to operate, and the fabric often gets caught
It has a double zipper that can be opened and closed from both ends to allow for easy ventilation around the chest
The short zipper also makes it difficult for air to get in and out, which can be a concern when it gets stuffy inside in hot summers. The stitched-through baffle structure allows warm air to escape more easily than a box structure, and the double zipper design ensures breathability depending on the temperature, which is impressive, but I still feel a little disappointed that there wasn't a zipper at the bottom to allow for a little more ventilation
Insulation: Lightweight yet warm thanks to premium goose down and TILT technology that minimizes heat loss
The main fabric is made of Atmos™ recycled nylon, a 10-denier ultra-fine yarn. It's tightly woven and treated with a durable water-repellent finish, making it extremely thin and lightweight without sacrificing durability. The filling is made of environmentally friendly, top-quality 900FP RDS-certified European goose down, sandwiched between our proprietary "TILT" (Thermo-Ion Lining Technology) lining, providing maximum warmth with minimal weight. Plus, it's treated with Nikwax for superior resistance to moisture and water
The "TILT" lining is a fabric that has become familiar in Rab's recent ultra-lightweight down sleeping bags and down jackets, offering excellent insulation per weight and featuring a distinctive metallic texture
The unique TILT lining coats each fiber with titanium, reducing heat loss without sacrificing breathability
TILT uses a special technology to coat each fiber with titanium. This allows radiant heat to be reflected back into the garment, minimizing heat loss without impairing the breathability of the fabric itself (according to Rab, radiant heat loss is reduced by up to 30% compared to normal conditions). This means that even with the same amount of down, the warmth can theoretically differ by as much as 30% depending on whether or not the fabric is used
I tried sleeping in a tent in April (around 5°C) with the Ultrasphere 4.5 mattress, which has an R-value of 4.3. As soon as I got into the sleeping bag, I felt the warmth inside so quickly that I wondered if it was generating heat from the inside, and thanks to the highly insulated mattress, there was absolutely no cold air coming from the floor. Despite the amount of down, which is by no means generous, I was still comfortably warm throughout the night. It weighs just 330 grams on its own, but when combined with the mattress, it achieved a minimum temperature of 0°C, and I realized that its specs are no joke
The foot area has a three-dimensional baffle structure that conforms to the shape of your feet, minimizing cold spots
However, it's important to note that this sleeping bag doesn't necessarily provide the same warmth as a mummy-style sleeping bag that meets the EN13537 or ISO23537 minimum temperature limit of 0°C. The Mythic Ultra 120 Modular only achieves Rab's proprietary sleep limit temperature of 0°C when used with an air mattress with an R-value of 4 or higher. Naturally, a mummy-style sleeping bag that meets the minimum temperature limit of 0°C on its own (such as the company's Mythic Ultra 180) will feel warmer than this model.
It's a given that the limit of how cold you can tolerate will vary depending on the mattress you use in combination with it, as well as the user's constitution and experience, but personally, from my own experience, if I were a beginner tent camper who had never slept in a particularly cold place, and suddenly had to sleep in a place where the temperature dropped to 0°C overnight using this sleeping bag and mat set, I can't really imagine being able to withstand the cold. For me, familiarity and mental preparation are quite important when it comes to camping outdoors
Since there is no padding on the back, the performance of the mattress directly affects how cold your back feels, so you need to be very careful about that as well
In any case, no matter what type of sleeping bag you use, it's important to remember not to assume that you can use it just at the lowest possible temperature (0°C in this case), but to allow for a margin of at least 5°C above the expected lowest temperature, and to prepare a mattress with ample insulation and warm clothing and equipment just in case
Combine it with the simultaneously released "Ultrasphere 4.5 Sleeping Pad" to create a lightweight and compact sleeping system weighing under 700g
The Mythic Ultra 120 Modular can be compressed quite compactly by placing it in the included compressible roll-top storage bag. This is another important point I like, so I'll explain it in detail: it's important that it's a large storage bag that can be compressed, rather than being forced into a small stuff sack. A fully compressed, hard bag tends to leave gaps when packing, so it's nice to have a large stuff sack that allows you to pack it in a fluffy state with a little room to spare. Incidentally, it's also nice that a large storage bag is provided for storage
The large compression stuff sack (left) is a roll-top type that allows you to adjust the compression level after packing the sleeping bag. In reality, it can be compressed even more than it appears in the photo. A large storage bag is also included (right)
Due to its versatile construction, this sleeping bag can be attached to many sleeping pads from other manufacturers. According to Rab, when used with a mattress with an R-value of 4 or higher, it can withstand temperatures down to around 0°C. Therefore, it is assumed that even lower temperatures can be achieved with a mattress with even better insulation
By the way, when combined with the lightweight, highly insulated air mattress "Ultrasphere 4.5" released by Rab at the same time, it is possible to cope with low-temperature environments of around 0°C with a sleeping system weighing just 700g. Of course, combining it with your current sleeping pad is also effective, but if you are looking for a more streamlined sleeping system that can be used in a wide range of three seasons, this is likely the best combination
Summary: The careful design that minimizes weight while maintaining minimum comfort may be the optimal solution for modern minimalists
What surprised me most about using it was how warm it was, even though it was so light and compact. With a thin pad, it's perfect for warm spring and summer, and when combined with a pad with a higher R-value, such as the Ultrasphere 4.5 Sleeping Pad, you can efficiently build a safe sleeping bed suitable for low mountain climbing from autumn to early winter, all with an unimaginably light and compact load
It's obviously perfect for hiking, alpine climbing, bikepacking, fastpacking, and other activities where lightness and speed are a priority, but even if lightness is prioritized, comfort isn't sacrificed in any way. In fact, the mattress is integrated into the bag, and you can easily create a pillow, making it even more comfortable to sleep in within the appropriate temperature range than a regular sleeping bag. Of course, there's a risk of a sad night's sleep if the mattress is thin or you forget the mattress
Although it is a little pricey, it is lightweight, compact, comfortable, and comes with the generous warranty of a major brand, making it a mattress that can be recommended to everyone, from veteran mountain climbers to ultralight hikers and tent camping beginners. Be sure to check it out in store
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