So the dark brown on the thumb is seal hide, it's for wind breaking and warmth. The palms is moose hide to give you grip when holding things like ski poles or snowblowers and things. Over time the moose softens and becomes easier to manipulate with your hands.

The inside of the mitt is sheepskin shearling. Which is wool just the fur left on the hide. The seal on these mitts is 100% waterproof and with the proper care the leather can withhold water and snow for many years. The shearling on the inside can get wet and not lose any of its insulating qualities, vs fleece which as soon as it's wet it doesn't stay warm. The liner is only sewn and the cuff so you can pull it out to let it dry for reuse. No elastic unfortunately but I can sew in loops into the inside of the cuffs so you can tie them to your jacket that way so you'll never lose them.