Anyone who spends time in the mountains, even on a single day hike, knows how quickly conditions can change. Blue skies can turn into a storm in a matter of minutes, the wind can pick up, and temperatures can drop dramatically. In situations like these, the piece of gear that often makes the difference between a comfortable outing and a miserable experience is a shell jacket.

In this guide, we'll explain how shell jackets work, the different types available, and the key technical features to consider before buying one. Understanding these factors will help you choose the right jacket for your adventures, without paying for features you'll never need or, conversely, finding yourself unprepared when the weather turns.

Why you need a shell jacket?

A shell jacket serves two main purposes: it prevents water from penetrating from the outside while allowing moisture vapor generated by the body to escape. A quality shell also provides effective wind protection, reducing heat loss caused by wind chill. Many models also offer an additional barrier against abrasion, branches, rocks, and minor impacts, making them particularly useful on technical trails and in alpine terrain.

In short, a shell jacket doesn't keep you warm. Its role is to manage the microclimate between your body and the external environment, keeping you dry from both rain and sweat.

The Shell as the Third Layer in a Layering System

In technical mountain apparel, a shell jacket is part of a layering system, typically made up of three components:

- Base layer: worn next to the skin, designed to move moisture away from the body.
- Mid layer: provides insulation and warmth, usually through fleece, merino wool, synthetic insulation, or down.
- Outer layer (shell): protects against external weather conditions.

This modular approach allows you to adjust your clothing to changing conditions by adding or removing layers as needed, rather than relying on a single all-purpose garment that performs only moderately well in every situation.

Shell Jacket vs Rain Jacket: What's the Difference?

A standard rain jacket, typically used in urban environments, is designed primarily to keep water out. Breathability is often a secondary concern because physical exertion is generally limited.

A Trekking or Alpinsim shell, on the other hand, is built for sustained activity. It must strike a balance between waterproofness and breathability; otherwise, perspiration trapped inside the jacket can leave you as wet as the rain outside.

For this reason, technical shells use advanced membranes and fabrics, often enhanced with a durable water repellent (DWR) finish, fully taped seams, water-resistant zippers, and adjustable hoods engineered for active use.

This level of weather protection and technical performance is what makes a product Weather-Ready, our standard for reliable protection from the elements.

What Is a Hardshell and When Should You Use One?

A hardshell is a fully waterproof shell jacket built with laminated membranes designed to keep water out even during heavy rain or intense snowfall. In our collection, we use both GORE-TEX® membranes and our proprietary PFAS-free Prometeo® membrane to deliver high levels of waterproofness and breathability while reducing environmental impact.

A hardshell is the ideal choice for situations where weather conditions may become severe: alpine environments, high-altitude treks, mountain thunderstorms, or multi-day adventures where reliable protection is critical.

The trade-off is comfort. Because hardshell fabrics are less elastic, they can feel more restrictive during prolonged, high-intensity activity.

What Is a Softshell and When Should You Choose One?

A softshell is softer, stretchier, and more breathable than a hardshell, but offers lower waterproof protection. It handles light rain, wind, and damp conditions well but is not designed for prolonged exposure to heavy rain.

In return, it provides greater comfort, improved freedom of movement, and better moisture management. These characteristics make it an excellent choice for activities such as climbing, ski touring ascents, or hiking in stable or only slightly unpredictable weather.

Many softshells also provide light thermal insulation, partially overlapping with the role of a mid layer. Combined with thermo-adaptive materials, this makes them particularly effective in variable mountain conditions, where temperatures, weather, and intensity levels can change quickly.

Hardshell or Softshell: Which One Should You Choose?

The right choice depends on three key factors:

• The weather forecast
• The expected level of exertion
• The altitude and environment

For day hikes in stable conditions with a low chance of heavy rain, a softshell generally offers superior comfort. For multi-day treks, alpine routes, or any outing where the weather could deteriorate quickly, a hardshell remains the safer choice, even if it sacrifices some comfort during intense effort.

Many experienced hikers carry both: a softshell for active movement and a packable hardshell stored in their backpack as emergency protection.

Beyond technical specifications, garment construction also plays a crucial role. Products developed with our Ergo-Fit standards are engineered to follow the body's natural movements, reducing restriction and improving comfort during dynamic outdoor activities. This ergonomic design helps maintain freedom of movement, whether you're reaching, climbing, or carrying a backpack over long distances.

Waterproof Rating: Understanding the Hydrostatic Head

The waterproofness of a fabric is measured by its hydrostatic head, expressed in millimeters (mm).

This value represents the height of a theoretical column of water that the material can withstand before water begins to penetrate through the fabric. In practice, the higher the hydrostatic head, the greater the pressure the fabric can resist. This becomes important not only during heavy rainfall, but also when additional pressure is applied to the garment, for example when sitting on wet ground, kneeling on snow, or carrying a backpack whose shoulder straps compress the fabric.

Although hydrostatic head is expressed as the height of a water column, laboratory testing does not involve physically stacking water to that height. Instead, the corresponding pressure is applied to the fabric and progressively increased until water penetration occurs. This allows waterproof performance to be measured accurately and consistently under controlled conditions.

All waterproof performance values reported by Montura are measured according to the UNI EN 20811 standard, an internationally recognized hydrostatic pressure test used to determine a fabric's resistance to water penetration and to ensure comparable waterproofness ratings across different materials and garments.

7,000 mm, 15,000 mm, or 20,000 mm: What Do They Mean?

As a general guideline:

• 2,000-7,000 mm: Suitable for occasional use, and high-aerobic activities in light rain. Common in softshells and entry-level hiking apparel.

• 7,000-15,000 mm: Recommended for regular hiking and trekking, offering reliable protection in moderate to prolonged rain.

• 20,000 mm and above: Designed for severe weather conditions, high-altitude environments, mountaineering, and extended exposure to heavy rain.

Keep in mind that waterproof ratings alone don't tell the whole story. Fully taped seams, waterproof zippers, and protective storm flaps all contribute significantly to real-world performance.

Breathability: Understanding MVTR and RET Ratings

Breathability measures a fabric's ability to release moisture generated during physical activity. The two most common measurement systems are:

• MVTR (Moisture Vapour Transmission Rate)

measures the amount of water vapour that can permeate through a fabric over a 24-hour period and is expressed in g/m²/24h. This parameter is commonly used to assess a membrane's ability to transport perspiration away from the body, thereby contributing to thermal comfort during high-output activities. Higher MVTR values indicate more efficient moisture management and reduced accumulation of internal humidity.

Montura measures breathability according to the JIS L 1099 B-1 standard, a widely recognized test method for determining moisture vapour transmission rates in waterproof and breathable fabrics. High-performance shell fabrics typically range from 10,000 to 20,000 g/m²/24h, while premium technologies may exceed these values.


• RET (Resistance to Evaporative Heat Transfer)

RET measures resistance to moisture transfer. Unlike MVTR, lower values indicate better breathability:

- RET under 6: State-of-the-art breathability
- RET 6-13: Excellent breathability
- RET 13-20: Optimal performance
- RET above 20: Good breathability

Because MVTR and RET are different measurement systems, comparisons should only be made between products using the same metric.

Weight and Packability

For hiking and trekking, the weight and pack size of a shell jacket can be just as important as its protective performance, especially when it spends most of the day inside your backpack.

Lightweight shells designed for fast hiking and high-output activities typically weigh less than 300 g and pack down to roughly the size of a water bottle. More robust mountaineering-oriented models often exceed 400g, providing increased durability and protection in exchange for additional weight.

The right balance depends on how and where you intend to use the jacket.

Fabric Durability and Long-Term Performance

An often-overlooked factor is the durability of the outer fabric.

Heavier-duty fabrics offer greater resistance to abrasion and tearing, making them ideal for frequent use, heavy backpacks, and demanding terrain. Lighter fabrics prioritize reduced weight and improved packability, making them popular for fast-paced activities where every gram matters.

The external DWR (Durable Water Repellent) PFAS Free treatment also plays an important role. Over time and after repeated washing, its effectiveness gradually decreases. Proper care and periodic reproofing help maintain reliable protection against light rain and moisture.

Shell for Day Hiking and Trail Trekking (Hiking)

For a day out on the trail, generally referred to as hiking, with typically stable weather, a shell with a hydrostatic head from 7,000 to 15,000 mm is more than enough.

In this context, it's worth prioritising lightness and packability, so it can be comfortably carried in the backpack even when you don't need to wear it, without giving up good breathability on the more demanding climbs.

Montura community's favourite shell for hiking:
Men: Shelter Jacket | Nordik Jacket | Magica Prometeo Jacket
Women: Shelter Jacket | Nordik Jacket | Magica Prometeo

Shell for Multi-Day Trekking and Long-Distance Walks

On a long-distance walk or a multi-day trek, where you can't count on a quick way back in case of bad weather, it's better to go for a more reliable shell in terms of water resistance, with a hydrostatic head starting at 15,000 mm and a robust construction (sealed seams, waterproof zippers).

A higher-denier fabric is also a good idea, as it holds up better under prolonged daily use and repeated contact with the backpack.

Montura community's favourite shell for Trekking and Long-Distance Walks:
Men: Magica Prometeo Jacket | Magica Pro Gtx Jacket
Women: Magica Prometeo Jacket | Magica Pro Gtx Jacket

Shell for Alpinism and High Altitude

In alpine environments and at high altitude, conditions can change quickly and severely: here a hardshell with a high hydrostatic head, starting at 20,000 mm, is recommended, capable of standing up to strong wind, heavy rain and wet snow.

In these contexts, the fabric's mechanical strength and build quality matter just as much as waterproofing itself, since the garment is often in contact with rock, harness and gear.

Montura community's favourite shell for Trekking and Long-Distance Walks:
Men: Vertigo Gtx Pro | Vertigo 3L
Women: Vertigo Gtx Pro | Vertigo 3L

Shell for Ski Mountaineering and Winter Activities

For ski mountaineering and winter activities, the combination we recommend as the primary solution is a lightweight hardshell worn over a down jacket: during the ascent, the down jacket comes off and goes in the backpack, while the outer shell protects against wind and moisture; at rest stops and on the descent, the down jacket goes back on, over or under the shell depending on temperature, providing immediate insulation without losing heat.

A softshell remains a valid option on milder days or more dynamic ascents where freedom of movement matters most, but in winter, at low temperatures, the shell-plus-down-jacket combination manages heat and cold more effectively, especially during breaks.

Montura community's favourite shell for Ski-Touring and Winter Activities:
Men: Magica Prometeo Jacket | Magica Pro Gtx Jacket | Skisky Evo Hooded Jacket
Women: Magica Prometeo Jacket | Magica Pro Gtx Jacket | Skiski Evo Hooded Jacket

Choosing a mountain shell jacket isn't about finding the highest waterproof rating or the most advanced fabric on paper. It's about finding the right balance of waterproofness, breathability, weight, durability, and comfort for the way you actually use it.

Understanding these technical parameters will help you read product specifications more critically and select the shell that best suits your adventures, whether you're heading out for a short day hike or embarking on a multi-day trek in the mountains.