The Merrell Siren 4 Thermo Mid Zip WP women's winter boots are uniquely engineered for female feet, providing comfort, support, and stability even on the longest hikes. With 200 g of insulation for warmth and protection and now equipped with added SOLARCORE® insulation, a lightweight insulation material initially designed for NASA, you never have to worry about your feet getting cold. The all-new medial zipper provides easy on and off while the Merrell waterproofing on the upper will keep your feet dry. With Vibram® IceTrek® outsole, traction remains consistent under the wettest, most slippery conditions thanks to the Vibram® traction lugs for enhanced grip on uneven terrain.