Which sleeping bag liner should I choose?

This is a hugely personal choice, and can't be answered in a single quick answer.

A really basic primer looks like this: the Silk, Silk/Cotton, and Expander liners are aimed primarily at travellers. They can be used for backpacking and will add some warmth, but not tons.

The Coolmax liners are designed for sleeping bags in warm and humid weather but are also great for travellers who like a more t-shirt like feel for their liner. Consumers based in the USA can also purchase Insect Shield-treated versions of the Adaptors which offer great protection against certain insects.

The Thermolite liners are made for increasing the warmth of your sleeping bag in colder temperatures. The warmer ones can be used as standalone sleeping bag substitutes in warm weather.

If you have ever tried a liner and found it to be constrictive, we would direct you to the Adaptor, Reactor, or Expander series – all three are made of really stretchy fabric.