Fleece & Mid-Layer Buying Guide

A midlayer is the insulating core of your outdoor layering system, designed to be worn over a base layer and under an outer shell. Its primary role is to trap body heat while managing moisture, ensuring you stay warm without overheating during activity. Think of it as your temperature regulator. It balances warmth and breathability by allowing sweat vapour to escape to your outer layers, preventing dampness that can lead to chilling. 

• Insulation: Midlayers create a warm air barrier around your body, using materials like fleece, down, or synthetic fibers to retain heat.

• Moisture Management: Breathable fabrics (e.g., Polartec fleece, merino wool) wick sweat away from your skin, keeping you dry during high-exertion activities like hiking or skiing.

• Adaptability: Midlayers can be added or removed as conditions change, making them ideal for stop-and-go activities like mountaineering or trail running.

Fleeces are highly versatile and available in a wide range of thicknesses making them a great choice as a mid-layer. Thinner fleeces are very practical, quick drying and breathable, making them a good option for high-output activities such as hiking in cold weather. Synthetic fleece material is also hydrophobic, which means it repels water and dries really fast, and it’s fluffy construction helps to trap air and retain heat from the body. In cold conditions where you are standing still or inactive, a thicker mid-to-heavy weight fleece will be better suited to make sure you keep sufficiently warm. 

Although fleeces have great insulating qualities, on the downside it’s worth pointing out that fleeces can weigh more than other forms of mid-layer insulation and aren't as compressible so can take up more room in your pack. Fleeces are also prone to pilling (when the fibres start clumping together), which makes it less insulating over time, and doesn't look so great, either.

While merino wool is often celebrated for its exceptional performance as a base layer, thicker merino wool fabrics also make excellent mid-layers. The natural crimp and loft of merino fibres provide effective insulation by trapping warm air close to the body, helping to regulate your temperature in cooler conditions without overheating. Unlike synthetic materials, merino wool is a renewable, biodegradable fibre, making it a more environmentally friendly and sustainable choice for those looking to reduce their outdoor gear’s ecological footprint.

One of the standout features of merino wool is its breathability - it efficiently wicks moisture away from the skin while allowing air to circulate, keeping you dry and comfortable during both high-output activities and periods of rest. Additionally, merino wool’s natural anti-microbial properties help prevent the buildup of unpleasant odours, meaning you can wear your mid-layer for longer between washes - a huge advantage on multi-day trips or when access to laundry facilities is limited.

Merino mid-layers also tend to be soft and comfortable against the skin, minimising itchiness often associated with traditional wool. Whether you’re hiking, skiing, or simply enjoying a brisk walk, a merino wool mid-layer offers a versatile, eco-conscious option that combines warmth, comfort, and odour resistance in one natural package.

A softshell is a woven, stretchy jacket typically crafted from nylon or polyester blends, engineered to strike the perfect balance between a fleece’s breathability and a hardshell’s weather resistance. Designed for high-intensity activities like climbing, ski touring, or fast-paced hiking, softshells excel in unpredictable conditions where mobility and comfort are key. Their durable, abrasion-resistant exterior shrugs off light rain, wind, and trail debris, while a fleece-lined interior retains warmth and wicks sweat, keeping you dry during exertion.

While softshells can often serve as an outer layer in dry or drizzly weather, their limited windproofing and water resistance (compared to hardshells) means they’re best paired with a waterproof jacket in prolonged downpours or gales. When the weather turns severe, layering a hardshell over your softshell transforms it into a high-performance midlayer that manages moisture trapped inside the hardshell, preventing clamminess.

Key Benefits:

• Stretch and Mobility: Articulated seams and elastic fabrics allow full range of motion for scrambling or skiing.

• Temperature Regulation: Breathable enough for uphill climbs, yet warm enough during rest stops.

• Durability: Reinforced shoulders and hoods withstand pack straps and rough terrain.

Ideal for mixed conditions, softshells are the go-to choice for adventurers who prioritise comfort and adaptability over absolute waterproofing.

An insulated jacket is the perfect mid-layer for extremely cold days. They work by trapping and retaining warm air in the space between down filaments or synthetic polyester strands. Insulated jackets are the warmest mid-layer and offer the best warmth-to-weight ratio. They're also the easiest to pack away when not needed thanks to their compressible fill. Whether you choose a down or synthetic insulated jacket will depend on the conditions you'll be using it in. Check out our guide on How To Choose An Insulated Jacket.

When selecting a midlayer, construction details play a critical role in how effectively you can regulate your body temperature. Hoods add valuable warmth for your head and neck, but they can create bulk or overlap awkwardly when layered under a hardshell’s hood. Opt for a low-profile design or a zip-off hood if you frequently wear a shell, ensuring compatibility across your layering system.

Ventilation options are equally crucial. Midlayers with full or half-zip fronts allow you to release excess heat quickly during high-exertion activities like uphill hiking, without needing to remove the entire layer-a game-changer compared to pullover styles like wool jumpers. Look for pit zips or mesh-lined panels in synthetic insulated jackets for targeted airflow.

Fit and adjustability also matter:

• Tailored cuts reduce bulk under shells, while articulated sleeves enhance mobility for climbing or skiing.

• Elasticated hems and adjustable cuffs help seal in warmth during rest stops.

• Layering-friendly fabrics, such as lightweight fleece or stretchy softshell materials, prevent restriction when worn over a base layer.

Pro Tip: Test midlayers with your existing gear-what works for alpine climbing (e.g., a slim, hoodless fleece) might feel restrictive under a ski shell. Having a versatile quiver-from breathable grid fleeces to insulated synthetic jackets ensures you’re prepared for any adventure, in any conditions.

Layering is the best way to keep warm because it traps air between each layer, so having the right, adaptable layers is much more effective than having one thick jacket. A basic layering system consists of a base layer, mid-layer and outer layer, and they're all as important to get right as each other.

Check out our Layering System Guide, Base Layer Buying Guide and our Waterproof Buying Guide for more info.