The Sea To Summit Thermolite Reactor Midweight Sleeping Bag Liner offers an ideal balance of warmth, packability, and versatile performance for backcountry travellers. Engineered to boost your sleep system's thermal efficiency, this liner utilises Thermolite Pro technology featuring infrared-absorbing ceramic pigments combined with hollow-core fibres to actively trap body heat and reflect it back to the sleeper. Constructed from a soft stretch knit fabric, it moves with your body during the night, while integrated arm openings provide maximum versatility—allowing you to read, use devices, or adjust gear without exiting your cozy cocoon.

Perfect for backpacking, cycle touring, and paddle touring, this liner can be paired with your sleeping bag to enhance warm-weather comfort or used on its own as an ultra-lightweight summer sleeping option. Practical touches include an easy-to-use fitted hood, snap connectors that secure the liner to your sleeping bag to prevent twisting, and HeiQ Fresh odour control to keep your gear smelling fresh night after night. Maintenance is entirely hassle-free since the fabric is quick-drying and easy to clean, preserving your primary sleeping bag from dirt, oils, and sweat.

Built with sustainability in mind from recycled fibres and bluesign-approved materials, it packs away effortlessly into its included stuff sack for seamless transport.

Key Features:

  • Regular Size: With a length of 193cm, recommended for users with a maximum height of 185cm.
  • Thermolite Pro Insulation: Integrates infrared-absorbing ceramic pigments alongside hollow-core fibres to reflect radiated warmth directly back to your body.
  • Ergonomic and Adaptable Design: Features a tailored technical shape paired with a snug fitted hood and built-in arm openings for effortless mobile convenience inside your tent.
  • Stretch Knit Comfort: Soft, flexible stretch knit construction offers unrestricted movement, ensuring a non-restrictive, natural sleep experience.
  • Long-Lasting Freshness: Treated with HeiQ Fresh odour control to eliminate bacteria-causing odours across extended wilderness excursions.
  • Integrated Sleep System Compatibility: Equipped with built-in snap connectors that lock directly into compatible Sea To Summit sleeping bags to eliminate bunching.
  • Eco-Conscious Construction: Sustainably crafted using recycled fibres and bluesign-approved materials.
  • Convenient Care and Transport: Exceptionally quick-drying and easy to clean to safeguard your bag, and compresses neatly inside a dedicated stuff sack (included).
The Sea To Summit Thermolite Reactor Midweight Sleeping Bag Liner boosts the thermal insulation of your sleeping bag by using hollow-core fibres combined with ceramic pigments that capture body heat and radiate infrared energy back toward you.
Yes, in warm weather or muggy climate conditions, the Sea To Summit Thermolite Reactor Midweight Sleeping Bag Liner can function as a standalone, ultra-lightweight sleeping cover or bed sheet.
Built-in arm openings in the Sea To Summit Thermolite Reactor Midweight Sleeping Bag Liner allow you to extend your arms outside the liner to read, operate devices, or adjust equipment without losing the body warmth retained inside the main compartment.

Brand : Sea To Summit

SKU: S2ST-053302

Model # : 053302

Barcode : 9327868169825  (AD-2)

Weight : 350g

Dimensions : 193 x 80cm

Packed Size : 19 × 11.5 × 11.5cm

Recommended User Height : 185cm

Liner Material : 100% Post-Consumer Recycled Polyester

Stuff Sack Material : 100% Polyester

Free shipping on orders over $140 to Australia*
Shipping on small orders (under $140) only $9.95
Shipping on all orders to NZ only $9.95
Express shipping to Australia & NZ only $15

Standard Shipping (AU) – FREE on orders over $140 and $9.95 on orders under $140. Orders are dispatched within 1 business day. Click here for shipping delivery times

Select ‘Standard Shipping – Auspost Only’ if you would prefer your parcel is sent with Auspost. Otherwise it will be shipped with any of our available carriers. Auspost Only shipping is not available on some very heavy/bulky orders.

Express Shipping (AU/NZ) – Need it faster? Express Shipping is available for $15. Express Shipping is not available on heavy/bulky orders. Orders placed before midday on business days are usually dispatched same day (otherwise within 1 business day). Delivery times in the table below.

Click and Collect – Shop online and collect in our Milton, Brisbane store, free for all orders. Orders are usually ready within 2 hours (during opening hours). Click here for address and opening hours.

Terms and conditions apply, click here for a full overview of our shipping policies

Manufacturing defects covered, replaced or repaired if soon after purchase.

  • If you have selected the wrong product/size for you, or want to exchange/return for any reason except for warranty or our error, this is referred to as a 'change of mind' return.
  • Not all products are eligible for change of mind returns (click here for excluded products).
  • Once you submit a Return Request, we will provide return instructions via email (along with a prepaid return label if applicable). Please wait to receive this before returning any items (Try 2 Anything excluded)
  • Change of mind returns can be resolved by your choice of exchange, full store credit, or a refund. Refunds are subject to a $19.95 admin fee.

For a full overview of our returns and warranty policies, see Returns and Warranties

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