With 25 years of Merrell's women's-specific fit, the Siren 4 Thermo is uniquely engineered to cradle the distinct contours of female feet, providing comfort, support, and stability even on the longest hikes with added insulation for warmth and protection. FEATURES • Waterproof membrane seals out water and lets moisture escape • Protective shell keeps feet dry • Waterproof suede leather upper • 100% recycled laces and webbing • Bellows tongue keeps out debris • 100% recycled fleece lining • 100 grams Primaloft® Gold Eco Series synthetic insulation • Rock plate for protection • FloatPro™ Foam midsole for lightweight comfort that lasts • Vibram® Icetrek outsole designed to provide the improved grip on very cold, icy, or snowy surfaces • Drop: 8mm • Lug: 5mm