When I’m snowshoeing, hiking in snowy conditions, and mountaineering, I keep my ankles and boots dry and prevent snow or rocks from slipping in with my Mountain Hardwear Women’s Gaiters.
They have a nice Velcro closure, which works surprisingly well, a sturdy strap to secure them under your boots, and are breathable, so my legs aren’t sweating on sunny days.
They work well in very cold conditions too. I’ve used them in deep powder last season in the Sierra Nevadas and they did their job well!