REI Midweight Fleece Bag Liner

I like this liner a lot. It can be compressed small, and comes with its own stuff sack. Can double as an emergency bag on short hikes or just to leave in your car during the winter. The zipper on the side which allows you to turn it into a blanket is a huge plus. It's great to bring on a road trip where you might get a bit cold.

I used it once in a mummy bag so I obviously had some extra material at the feet, but this baby kept me warm and toasty, definitely increased my bag warmth by the degrees advertised (8 i believe?).

The weaknesses are basically in the material in that it doesn't breathe extremely well and tends to soak up moisture. It also is heavier than comparable silk liners, but at this price point it's a heck of a deal.