Swix Shield Split Mitt (women's)
Popular with cyclists, the Split Mitt gives you more warmth than a glove yet more dexterity than a full mitten. Waterproof and windproof, with a long stretchy cuff to keep drafts out even when your arms are extended.
Swix women's size guide (based on circumference of the hand):
Size S = 15.5 cm
Size M = 18 cm
Size L = 20.5 cm