For these mittens I took used wool sweaters and cut out pieces. There are 4 pieces: 2 for the palm of the hand, 1 for the front, and one for the cuff of the mitten. The insides are lined with fleece!
The top mittens are made to be more fitted. The brown and green mittens (lower) are a bit more chunky. The sizes have different purposes to me. The small are great to put on when going out and I love the bigger ones for shoveling snow or driving.
Just in the past few years I've had trouble keeping my hands warm. I have some really nice windproof gloves, but they don't always cut it when it's super cold outside. Mittens are the best for keeping fingers warm. It's good to have my fingers next to one another to produce extra body heat.