From Black Diamond:

Light, packable, Waterproof Overmitts are constructed with fully taped seams, and stretchy three-layer waterproof and breathable shell fabric. Cover your fleece, softshell or leather gloves to add total weather protection. Ideal for ski touring, winter climbing or backpacking in cold, mixed conditions, these simple mitts seal out the elements while you belay, climb, ski or hike.