When choosing a sleeping bag liner, start with the basics: fabric feel, packed size, ease of washing, and how you plan to use it. Some buyers want a liner mainly for camping, while others care more about hostel stays, train travel, or keeping a spare layer ready for overnight guests.
A good liner should feel comfortable against the skin, fit your packing style, and hold up to repeated use. Instead of chasing complicated features, most people are better served by a liner that is breathable, easy to clean, and simple to keep in rotation between trips.