Last Updated on July 24, 2026 by Daniel Globe
The Rab Mythic Alpine is an ultralight down jacket for climbers, mountaineers, ski tourers, and trekkers who want strong insulation without a bulky pack. Its 900-fill-power goose down and 10D Pertex Quantum shell give it an impressive warmth-to-weight balance, but the thin fabric and non-waterproof construction also create clear limits. This review explains the verified specifications, fit, weather protection, packability, sustainability claims, and the situations where another jacket may work better.
Quick Answer
The Rab Mythic Alpine is a strong choice for fast alpine trips where warmth, low weight, and packability matter most. It uses 140 g of 900FP hydrophobic goose down and weighs 313 g in a men’s medium. It blocks wind and sheds light moisture, but it is not waterproof or made for heavy abrasion.
Key Takeaways
- Verified weight: 11 oz (313 g) in a men’s medium, with 4.9 oz (140 g) of 900FP European goose down.
- Best use: Cold, weight-sensitive climbing, mountaineering, trekking, and ski touring.
- Weather limit: The Pertex Quantum shell is windproof and water-resistant, not waterproof.
- Fit: Slim and low bulk, with articulated sleeves and a 29.5-inch centre-back length in size medium.
- Main trade-off: The 10D shell saves weight but needs more care around rock, ice tools, sharp branches, and rough pack straps.
What Is the Rab Mythic Alpine Jacket?
The Rab Mythic Alpine Down Jacket is a slim, high-loft layer designed for climbing, mountaineering, skiing, and trekking. Rab uses a 10D recycled Pertex Quantum nylon ripstop outer and lining, 900FP European goose down, and low-bulk stitch-through baffles. The goal is simple: give you a large amount of insulation in a jacket that remains light, mobile, and easy to pack.
The jacket includes a down-filled hood with a partly elastic opening and stiffened peak, a lightweight YKK VISLON front zip, two concealed zipped hand pockets, partly elastic cuffs, and a dual-sided rear hem adjustment. Pre-curved, articulated sleeves improve reach while climbing. Rab also supplies a lightweight stuff sack.
| Fit | Slim |
| Weight | 11 oz / 313 g, men’s size medium |
| Down | 900FP European goose down with Nikwax fluorocarbon-free hydrophobic treatment |
| Fill weight | 4.9 oz / 140 g, UK men’s size medium |
| Shell | 10D recycled Pertex Quantum nylon ripstop, 28 gsm, with fluorocarbon-free DWR |
| Back length | 29.5 in / 75 cm, men’s size medium |
| Product code | QDB-45 |
Rab Mythic Alpine Jacket Warmth and Weight
The Mythic Alpine’s strongest point is its combination of 140 g of high-fill-power down and a 313 g total weight. Fill power measures how much space a given weight of down can loft into. A higher number usually means the down can provide more loft for less weight, but fill power alone does not tell you the jacket’s full warmth. Fill weight, baffle design, fit, wind, moisture, activity level, and your personal cold tolerance also matter.
Note: Rab does not publish a temperature rating for the Mythic Alpine. Claims that it will keep every user warm at freezing, below freezing, or on a winter expedition are not reliable without considering layers, wind, exposure time, and individual cold tolerance.
Warmth-to-Weight Ratio
The 900FP European goose down delivers a high amount of loft for its weight. Rab places square baffles around the core to support warmth and uses regular baffles on the sleeves to improve mobility. The stitch-through construction reduces weight and bulk, but every stitched line compresses the insulation. That makes this design lighter and more breathable than a box-wall expedition jacket, while also creating more potential for heat loss at the seams.
The verified specification is 140 g of 900FP down inside a 313 g jacket, so nearly half of the jacket’s listed weight comes from its down fill.
The Mythic Alpine works best as a warm stop layer, camp layer, or cold-weather midlayer when low weight matters. During hard uphill movement, even a breathable down jacket can feel too warm and trap sweat. In those conditions, open the zip, remove the jacket, or switch to a more air-permeable active-insulation layer.
Ultralight Packability
High-fill-power down compresses well, and the jacket comes with a lightweight stuff sack. Rab does not publish an official packed volume, so claims that it always compresses to a grapefruit-sized bundle are too exact. The practical takeaway is that it packs much smaller than most heavier all-purpose down jackets and fits easily into a climbing or trekking pack.
Pro Tip: Use the stuff sack during travel, but store the jacket loose and fully dry at home. Long-term compression can reduce loft and make the down slower to recover.
Key Rab Mythic Alpine Jacket Features
The jacket focuses on warmth, mobility, and low weight rather than maximum durability or full storm protection. Its most useful features are the high-loft down, wind-resistant shell, articulated sleeves, adjustable hem, and low-bulk construction.
Premium Down Insulation
Rab uses 900FP European goose down with a Nikwax fluorocarbon-free hydrophobic treatment. Hydrophobic treatment helps the down resist moisture and dry faster than untreated down, but it does not make the insulation waterproof. If the down becomes saturated, it can still clump, lose loft, and provide less warmth.
Rab states that its duck and goose down is certified to the Responsible Down Standard. The RDS tracks down through the supply chain and applies animal-welfare requirements. This adds useful sourcing transparency, although it does not change the jacket’s weather performance.
Ultralight Pertex Shell
The 10D shell uses Pertex Quantum, a tightly woven, downproof fabric designed to be light, windproof, and water-resistant. Its DWR finish can shed brief light rain or dry snow. It is not a waterproof membrane, and the stitch-through seams are not presented as taped or waterproof.
Warning: Do not rely on this jacket as your only protection in prolonged rain, wet snow, or a severe alpine storm. Carry a waterproof shell and protect the thin 10D fabric from sharp rock, crampons, ice tools, branches, and open flames.
The shell is strong for its very low weight, but “durable” is relative. A 10D fabric saves grams and packs small, yet it is less forgiving than the heavier fabrics used on daily-use or expedition jackets. Wearing a shell over it can reduce wind exposure and protect it from abrasion.
Slim Alpine Fit
The slim cut follows the body closely and layers cleanly under a waterproof shell. Pre-curved, articulated sleeves improve arm lift, while partly elastic cuffs and the rear hem adjustment help reduce drafts. This fit is efficient for technical movement, but it leaves less space for thick fleece or synthetic midlayers than a regular or expedition cut.
The hood is down-filled and has a partly elastic opening with a stiffened peak. Rab does not describe this model’s hood as helmet-compatible on the product page and does not list an external hood adjustment. It may work under some helmets, but you should test the exact jacket size and helmet combination before depending on it in the mountains.
Rab Mythic Alpine Jacket Fit and Sizing
Use body measurements, not height alone, when choosing a size. Rab’s current product page shows sizes from XXS through 3XL, although stock can vary by market and colour. The official men’s size guide lists a medium for a 40-inch chest, 32-inch waist, and 34-inch arm length. A large corresponds to a 43-inch chest, 34-inch waist, and 35-inch arm length.
- Measure your chest just below the armpits.
- Measure your waist around the top of your hips.
- Measure arm length from the centre of your back, across the shoulder and bent elbow, to the wrist.
- Compare those measurements with Rab’s chart and account for the layers you plan to wear.
The current product page shows a 6-foot-1-inch model wearing a large, but that does not mean every person of that height needs a large. Choose your usual Rab size for a close fit over a base layer or thin fleece. Consider the larger size when you are between measurements or need room for a thicker midlayer. The verified centre-back length is 29.5 inches in size medium.
Rab Mythic Alpine Jacket Sustainability
Rab’s Material Facts table reports that the Mythic Alpine contains 39% recycled material by total product weight. The outer and lining are listed as 100% recycled polyamide, while the hydrophobic down is listed as 0% recycled. Rab also reports no intentionally added PFAS in the listed product components and says 57% of the energy used for product manufacturing came from renewable sources. The jacket is manufactured in Indonesia, and the published Material Facts version is dated March 2024.
These details are more useful than a broad “eco-friendly” label because they show both the improvements and the limits. The jacket still uses new animal down, zips and trims contain lower recycled percentages, and manufacturing still uses some non-renewable energy. Its RDS-certified down, recycled shell and lining, PFAS-free treatment, repair options, and long usable life can reduce impact, but no technical jacket is impact-free.
Weather Protection, Durability, and Limitations
- Not waterproof: It handles brief light precipitation but needs a waterproof shell for sustained wet weather.
- No official temperature rating: Warmth depends on wind, layers, pace, exposure time, food, fatigue, and personal cold tolerance.
- Thin 10D fabric: Excellent for low weight, but more vulnerable to punctures and abrasion than heavier shells.
- Stitch-through construction: Keeps weight and bulk down but can lose more heat through seam lines than box-wall construction.
- Slim fit: Works well under a shell but may feel restrictive over thick layers.
- Limited storage: You get two zipped hand pockets, with no chest pocket listed on the official specification.
How to Wash and Store the Rab Mythic Alpine
Correct care protects the down’s loft and the shell’s water-repellent finish. Follow the garment label first. Rab’s official down-jacket washing guide recommends a cool, gentle wash, thorough rinsing, and complete tumble drying on low to medium-low heat.
- Empty the pockets, close the zips, and turn the jacket inside out.
- Wash one item at a time with a down-specific cleaner or suitable non-biological soap. Do not use fabric softener.
- Run a cool, long, gentle cycle and rinse thoroughly.
- Support the wet jacket when moving it because wet down and internal baffles are vulnerable.
- Tumble dry on low to medium-low heat. Pause every 20 to 30 minutes to shake the jacket and separate clumps. Clean dryer balls can help.
- Keep drying until every baffle is fully dry and lofty, then air the jacket before storage.
- Store it uncompressed in a cool, dry place.
Rab Mythic Alpine Jacket vs. Other Down Jackets
The Mythic Alpine is not automatically “better” than every lighter or heavier jacket. It carries more down than some ultralight rivals, while other models use tougher fabrics, synthetic insulation in moisture-prone areas, a roomier fit, or more everyday features. Manufacturer weights can also use different sample sizes, so treat the table as a specification comparison rather than a controlled warmth test.
| Jacket | Listed weight | Insulation | Main difference |
|---|---|---|---|
| Rab Mythic Alpine | 313 g, size M | 140 g of 900FP goose down, size M | High down fill in a slim, 10D alpine design |
| Mountain Hardwear Ghost Whisperer Hoody | 302 g, size M | 84 g of 800-fill RDS down, size M | Slightly lighter, with substantially less listed down fill |
| Arc’teryx Cerium Hoody | 338 g | 850-fill down plus Coreloft synthetic insulation | Hybrid insulation in moisture-prone areas and a 15D shell |
| Rab Microlight Alpine | 466.5 g, size L | 153 g of 700FP recycled down, size L | Heavier, regular-fit design aimed at broader year-round use |
Choose the Mythic Alpine when you want more insulation than a minimalist ultralight puffy without moving into a much heavier daily-use jacket. Choose the Ghost Whisperer when every gram matters more than fill weight, the Cerium when you value hybrid insulation in damp-prone zones, or the Microlight Alpine when everyday versatility and a regular fit matter more than minimum weight.
Who Should Buy the Rab Mythic Alpine?
It is a good match for:
- Climbers and mountaineers building a light layering system.
- Ski tourers who need a compact warm layer for stops and transitions.
- Backpackers who prioritise warmth and pack space over rugged fabric.
- Travelers who want a warm jacket that compresses into a small pack.
Consider another jacket if:
- You regularly hike through brush, scrape against rock, or use the jacket as a rough daily outer layer.
- You expect long periods of rain or wet snow without a waterproof shell.
- You need a roomy expedition fit for several thick layers.
- You want a clearly helmet-compatible, fully adjustable hood.
- You prefer synthetic insulation for repeated damp conditions and easier drying.
Frequently Asked Questions
Is the Rab Mythic Alpine suitable for winter mountaineering expeditions?
It can be useful for winter mountaineering as part of a complete layering system, but Rab does not give it an expedition temperature rating. Its slim fit, stitch-through baffles, and 10D shell differ from heavier box-wall expedition jackets. Match it to the route, forecast, exposure time, other layers, and your cold tolerance.
How packable is the Rab Mythic Alpine Jacket?
It is highly packable because of its 900FP down, low-bulk baffles, and thin 10D fabrics. Rab includes a lightweight stuff sack but does not publish an exact packed volume. Compress it for transport, then store it loose and dry between trips.
Can the jacket handle wet snow and light rain?
The Pertex Quantum shell and DWR finish can shed brief light rain or snow. The jacket is not waterproof, and wet down can lose loft. Add a waterproof shell for sustained precipitation or wet, windy conditions.
Is the hood compatible with ski or climbing helmets?
Rab lists a down-filled hood with a partly elastic opening and stiffened peak, but it does not label the hood as helmet-compatible or list an external adjustment. It may fit under some helmets. Test your exact helmet and jacket size before using them together.
What colors does the Rab Mythic Alpine Jacket come in?
Colors vary by season, country, and remaining stock. Check Rab’s current product page or an authorised retailer for the available options in your size rather than relying on an older colour list.
What temperature is the Rab Mythic Alpine rated for?
Rab does not publish a fixed temperature rating for this jacket. Your comfort depends on wind, humidity, activity, base layers, food, fatigue, exposure time, and personal cold tolerance. Use the insulation specifications and your own experience to build a safe layering system.
How should you wash the Rab Mythic Alpine?
Follow the care label. Use a cool, gentle cycle with a down-specific cleaner, rinse thoroughly, and tumble dry fully on low heat. Shake and separate the down during drying, and store the jacket uncompressed once it is completely dry.
Conclusion
The Rab Mythic Alpine delivers a rare combination of 140 g of 900FP down, a verified 313 g medium weight, and a slim design that packs easily under a shell. It is best for cold, weight-sensitive alpine trips where you can protect the 10D fabric and carry waterproof protection. It is less suitable as a rugged daily jacket, a stand-alone rain layer, or a guaranteed expedition parka. Choose it for warmth, mobility, and packability, while accepting the durability, fit, and wet-weather trade-offs that make such a low weight possible.
Sources
- Rab: Men’s Mythic Alpine Down Jacket — official weight, fill, fabrics, features, fit, and Material Facts.
- Pertex: Quantum fabric technology — windproof, water-resistant, downproof construction and DWR performance.
- Rab: Men’s size guide — body measurements and slim-fit definition.
- Rab: Down insulation explained — fill power, down composition, and Responsible Down Standard certification.
- Rab: How to wash a down jacket — cleaning, drying, and storage guidance.
- Official comparison specifications: Mountain Hardwear Ghost Whisperer, Arc’teryx Cerium Hoody, and Rab Microlight Alpine.