Sleeping bag liner SEA TO SUMMIT Reactor Fleeceweight R – fleece thermal liner, model Picante

The SEA TO SUMMIT Reactor Fleeceweight R – fleece thermal liner, model Picante is a soft fleece sleeping bag liner designed to increase warmth and comfort inside your sleeping bag. Lightweight and compact, this liner adds an insulating layer that helps retain body heat, protects the inner fabric of your sleeping bag from dirt and sweat, and can be used alone as a light blanket or hygiene layer when temperatures are mild. The rectangular / regular shape makes it compatible with many standard sleeping bags and easy to enter and exit.

Advantages

The fleece construction provides additional thermal insulation without adding significant bulk. Its soft surface improves sleeping comfort and reduces abrasion on the sleeping bag lining. The liner is quick to pack and unpack, and its shape and size allow it to be used as a standalone layer for hygiene in shared accommodation or as an added warmth layer in colder conditions. The material is breathable, helping manage moisture while maintaining a warmer microclimate inside the bag.

Suitable for

• Backpacking and multi-day hikes where lightweight insulation is needed
• Car camping and basecamp use for extra comfort and protection
• Travel and hostels where a personal hygiene layer is useful
• Cool-weather conditions where added warmth inside a sleeping bag is required

When it may not be suitable

The Reactor Fleeceweight R is not intended as a primary sleeping bag in very cold conditions; it supplements a sleeping bag rather than replaces a rated cold-weather bag. It will not provide significant waterproofing or windproofing, so in wet or very windy environments you should rely on a proper shell or tent for protection. For ultralight minimalist setups where every gram counts, a fleece liner may be heavier than alternative silk or ultralight synthetic liners.

Key specifications

• Material: lightweight fleece providing thermal insulation
• Shape: rectangular / regular for standard sleeping bags
• Use modes: liner for sleeping bag, standalone hygiene blanket
• Properties: breathable, soft interior surface, adds thermal layer
• Packability: compressible for travel and storage

How to use

Insert the Reactor Fleeceweight R liner into your sleeping bag with the fleece side next to your skin to maximise comfort and insulation. Zip or tuck the liner into the bag where compatible, ensuring it lies flat to avoid cold spots. When used alone, drape it as a light blanket or wrap around the torso for added warmth. After use, allow the liner to dry fully if damp before packing to prevent odour and maintain fabric performance.

What to consider before purchase

• Compatibility with your sleeping bag shape and zip location
• Required level of insulation versus weight for your trips
• Whether you need a liner primarily for hygiene, extra warmth, or both
• Care needs: fleece dries faster than many fabrics but should be stored dry

Usage recommendations

For best thermal performance, use the fleece liner in combination with a sleeping bag rated for the expected night temperatures; position the fleece against your body, and ensure the sleeping bag and liner are both dry before packing. In hostels or travel situations, use the liner as your primary hygiene layer to protect the sleeping bag from sweat and reduce laundering frequency.