Most sleeping bags are rather expensive so it makes sense to extend their lifespan. A sleeping liner is a great way to do this because it protects the inside of the sleeping bag from any dirt etc that you may have picked up during the day!
While many hikers carry a silk liner, I think it better to use a liner that also provides extra warmth – for when you need it.
The Thermolite Reactor sleep liner by Sea to Summit is made of synthetic insulation. It’s designed to provide warmth and doesn’t compromise on weight. I personally care about the latter because I often hike long distances with a heavy backpack. The material is also very comfortable and offers a duvet-like feel which is soft on the skin.
The Thermolite Reactor liner claims to add 15°C to the warmth of the sleeping bag. It weighs 400g but the size is pretty small. You can wash this item instead of the sleeping bag and I don’t believe this has any negative effect on the fabric.
While I always take this item on camping trips, it was also useful on the Camino de Santiago. After all, when the weather is warm, it’s often nicer to use a sleep liner as opposed to a sleeping bag. Either way, the Thermolite Reactor Liner gets a thumbs up from me and I believe it strikes the ideal balance between weight, comfort and warmth.