If you’re looking to push your adventures further into the chiller months without carrying a bulky, heavy sleeping bag, the Sea To Summit Thermolite Reactor Midweight Long Sleeping Bag Liner is your ultimate trail companion. 

Ideal if you value both performance and planet-conscious design, this cosy sleeping liner features advanced Thermolite Pro fabric with hollow-core fibres and infrared-absorbing ceramic pigments to capture and reflect your body’s natural warmth. 

Whether you are backpacking, cycle touring or trekking remote wilderness trails, this sleeping bag thermal liner can increase the warmth of your sleep system by up to 6°C | 11°F, effectively bridging the gap between seasons without adding non-essential bulk. Sea To Summit puts Bluesign approved and recycled fibres into action, ensuring you enjoy eco-friendly warmth on your next camping trip or adventure while being fast-drying and easy to clean. 

Stretch-knit fabric and generous arm openings ensure you never feel restricted while you sleep, while the technical shape and hood provide a cosy and comfortable fit. Beyond warmth, this sleeping bag thermal liner acts as a hygienic barrier, featuring HeiQ Fresh odour control, helping maintain your sleep system in like-new condition for longer.

Key Features:

  • Lightweight Warmth: The Thermolite Reactor transforms your existing sleep setup into a high-performance cold-weather system - fantastic for backpacking, camping, paddle touring and cycling touring.
  • Compatible With Sea To Summit Sleeping Bags: Shoulders feature snap connectors to help your entire sleep system work in harmony. 
  • Thermolite Pro Fabric: The next evolution of standard Thermolite with innovative hollow-core fibres and ceramic pigments to maximise thermal retention.
  • Thermal Boost: Designed to add up to 6°C | 11°F to a sleep system, making your current sleeping bag more adaptable for cooler environments.
  • Thermolite Eco Made: Being made from 100% textile waste, this is an environmentally preferable material without any compromise to durability or performance.
  • Stretch-knit Fabric: Allows you to move naturally and comfortably throughout the night.
  • HeiQ Fresh Odour Control: An advanced treatment that keeps the fabric fresh even after multiple nights of outdoor adventure - reducing the need to wash to extend its longevity. It’s also machine washable to make cleaning more effortless. 
  • Technical Shape And Fitted Hood: Delivers additional warmth and a cosy, comfortable feel at a minimal weight.
Yes, sleeping bag liners are worth it if you’re a regular camper and provide three key benefits; increased warmth, hygiene and gear care. Specialised materials from Sea To Summit like Thermolite Pro help keep you toasty when the temperature drops. Technologies like HeiQ Fresh create a barrier to protect your sleeping bag from odour, helping to increase its lifespan and encourage a restful night’s sleep to wake up fresh for adventure.
The Sea To Summit Thermolite Reactor Midweight sleeping bag liner is designed to boost thermal warmth by up to 6°C | 11°F, significantly increasing the versatility of your current sleep system when temperatures drop in the colder months.
Thermolite is considered one of the best materials for sleeping bag liners, with Sea To Summit Thermolite Eco Made offering the lightweight warmth of a traditional, high-quality synthetic thermal liner, while reducing your carbon footprint on the environment.

Brand : Sea To Summit

SKU: S2ST-053303

Model # : 053303

Barcode : 9327868169818  (AD-2)

Weight : 365g

Dimensions : 198 x 80cm

Packed Size : 11.5cm x 19cm x 11.5cm

Materials : 100% Post-Consumer Recycled Polyester

Stuff Sack : 100% Polyester

Fits Up To Height : 198cm

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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