---
title: "Sea To Summit Reactor Fleeceweight Liner"
name: "Sea To Summit Reactor Fleeceweight Liner"
brand: "Sea To Summit"
description: "The Sea to Summit Reactor Fleeceweight liner boosts your sleeping bag's thermal comfort by up to 8°C (14°F)."
handle: "sea-to-summit-reactor-fleeceweight-liner"
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locale: "en"
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currency: "EUR"
price: 79.9
price_formatted: "€79.90"
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category: "Sleeping bag liners"
category_path: "/c/sleep/sleeping-bag-liners"
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  - name: "Sea To Summit Reactor Fleeceweight Liner"
    url: "/p/sea-to-summit-reactor-fleeceweight-liner"
last_updated: "2026-07-08"
---

# Sea To Summit Reactor Fleeceweight Liner

Brand: Sea To Summit · Category: [Sleeping bag liners](/c/sleep/sleeping-bag-liners.md)
Liner size: Long, Regular, Short · Material: Thermolite All-Season EcoMade · Material composition: Polyester

## Offer

- Price: €79.90
- Availability: In stock
- Condition: New
- Buy on the website: [HTML product page](/p/sea-to-summit-reactor-fleeceweight-liner)

## Description

The Sea to Summit Reactor Fleeceweight liner boosts your sleeping bag's thermal comfort by up to 8°C (14°F). It's stretchy, soft to the touch, and has clever hand openings so it won't restrict your movement at night. The liner also protects your sleeping bag from sweat and dirt, extending its lifespan. Made from a combination of hollow Thermolite® fibers and warm grid fleece material.

## What makes this product special?

Up to 8 °C of extra warmth and total freedom of movement in a cozy fleece design.

material – a blend of hollow Thermolite® fibers and warm grid fleece (fleece with a grid structure), largely recycled (EcoMade), increases thermal comfort by up to 8 °C, can be used on its own as an ultralight summer sleeping bag, mummy shape, drawcord on the collar and hood, integrated arm openings and shoulder snaps for attaching to Sea To Summit sleeping bags, odor control via HeiQ Fresh treatment, travel bag (25 × 15 × 15 cm)

## Specifications

The Sea to Summit Reactor Fleeceweight Liner is a sleeping bag liner that **noticeably boosts your thermal comfort** while also serving as reliable **protection for your sleeping bag against sweat and dirt**, extending its lifespan. According to the manufacturer, it can **increase the temperature inside your sleep system by up to 8 °C**, while still keeping a good weight and packability.

In warm conditions, or in mountain huts and hotels, you can use the liner **on its own as an ultralight summer sleeping bag**. A big advantage of the synthetic material is that, unlike down, it doesn't lose its insulating properties even when damp. And once you're back from your trip, you can simply toss the liner in the washing machine.

The liner's mummy shape naturally follows the curves of your body and **fits perfectly inside any mummy-shaped sleeping bag**. You can easily adjust the collar and snug-fitting hood using the **drawcord**. A great feature is the **integrated arm openings** and shoulder snaps, which let you clip the liner onto Sea To Summit sleeping bags. That way you can keep the hood cinched snugly around your head while still having your hands free for reading or cooking.

The package also includes a handy **travel bag**, which lets you pack the liner down into a compact bundle measuring **25 × 15 × 15 cm**.

## Materials

The Reactor Fleeceweight Liner sleeping bag liner is made from a blend of hollow **Thermolite®** fibers and warm **grid fleece** (fleece with a grid structure). The materials used are largely **recycled** (EcoMade).

This specific structure effectively traps air in small pockets and **reflects body heat back to you**. The material has excellent **stretch**, easily **wicks moisture**, dries quickly, and is remarkably **pleasant to the touch**. The liner retains its great insulating properties for a long time, even in more demanding conditions.

Sea To Summit liners are treated with **HeiQ Fresh** technology, which contains no biocides and is highly effective at **controlling odor**. It uses a bio-based amino sugar polymer to neutralize body odor, so the liner stays fresh longer and you won't need to wash it as often.

If you're after a lighter, less warm liner, check out the [Reactor Midweight Liner](/p/sea-to-summit-reactor-midweight-liner).

## Specs

- Color: Red
- Liner size: Long, Regular, Short
- Material: Thermolite All-Season EcoMade
- Material composition: Polyester
- Packed dimensions: Ø 15 x 25 cm
- Weight: 400 g
- Brand: Sea To Summit

## Variants

- Sea To Summit Reactor Fleeceweight Liner - Regular · SKU 053402 · EAN 9327868169726 · €79.90 · In stock · Regular, Red
- Sea To Summit Reactor Fleeceweight Liner - Short · SKU 053401 · EAN 9327868169733 · €79.90 · Out of stock · Short, Red
- Sea To Summit Reactor Fleeceweight Liner - Long · SKU 053403 · EAN 9327868169719 · €84.10 · In stock · Long, Red

## Related

- [Sea To Summit Breeze Liner Mummy](/p/sea-to-summit-breeze-liner-mummy.md)
- [Sea To Summit Spark II](/p/sea-to-summit-spark-2.md)
- [Sea To Summit Silk Blend Liner Mummy](/p/sea-to-summit-silk-blend-liner-mummy.md)
- [Sea To Summit Spark III](/p/sea-to-summit-spark-3.md)
- [Sea To Summit Reactor Liner Mummy](/p/sea-to-summit-reactor-liner-mummy.md)
- [Sea To Summit Aeros Premium Pillow (2026)](/p/sea-to-summit-aeros-premium-pillow-2026.md)
- [Sea To Summit Reactor Fleece Liner Mummy](/p/sea-to-summit-reactor-fleece-liner-mummy.md)
- [Sea To Summit Aeros Ultralight Pillow (2026)](/p/sea-to-summit-aeros-ultralight-pillow-2026.md)

## Shipping and returns

- [Shipping and payment](/shipping-payment)
- [Returns](/return-order)

## Images

- ![Sea To Summit Reactor Fleeceweight Liner](https://media.gramino.com/medusa/STS-Reactor-Fleeceweight-Liner-1-01KX1BRGSNTWYC97WD2D8PAY63.jpg)
- ![Sea To Summit Reactor Fleeceweight Liner](https://media.gramino.com/medusa/STS-Reactor-Fleeceweight-Liner-2-01KX1BRH4C3N6R08PN1A0ZAGG4.jpg)
- ![Sea To Summit Reactor Fleeceweight Liner](https://media.gramino.com/medusa/STS-Reactor-Fleeceweight-Liner-3-01KX1BRHE65EW281NBVPVBRJM7.jpg)
- ![Sea To Summit Reactor Fleeceweight Liner](https://media.gramino.com/medusa/STS-Reactor-Fleeceweight-Liner-4-01KX1BRHSN2EQ073NNFBARMNQW.jpg)
- ![Sea To Summit Reactor Fleeceweight Liner](https://media.gramino.com/medusa/STS-Reactor-Fleeceweight-Liner-5-01KX1BRJ5YZJJTHNZS7XXBYW5G.jpg)
- ![Sea To Summit Reactor Fleeceweight Liner](https://media.gramino.com/medusa/STS-Reactor-Fleeceweight-Liner-6-01KX1BRJF7C76DDRNME1MCBMJ0.jpg)

## Identifiers

- SKU: 053402
- EAN: 9327868169726
- Handle: sea-to-summit-reactor-fleeceweight-liner
- Brand: Sea To Summit

This product is also available as [HTML](/p/sea-to-summit-reactor-fleeceweight-liner).

Category: [Sleeping bag liners](/c/sleep/sleeping-bag-liners.md) · [Sitemap](/sitemap.md)

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