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 200 grams of added insulation for warmth and protection. Now equipped with SOLARCORE® insulation, lightweight insulation material initially designed for NASA, you never have to worry about warmth. The all-new medial zipper provides easy on/off, a new improvement made directly from customer feedback. Merrell® waterproofing on the upper will keep your feet dry. With Vibram® IceTrek® underfoot, traction remains consistent under the wettest, most slippery conditions. For the first time ever incorporating Vibram® traction lug for enhanced grip on uneven terrain. Waterproof membrane seals out water and lets moisture escape Waterproof full grain leather and knit upper 100% Recycled laces and webbing Heavy-duty, Waterproof, YKK medial zipper for easy on and off Bellows tongue keeps out debris Protective and abrasion resistant rubber heel and toe cap 100% Recycled fleece lining Primaloft® Gold Eco Series synthetic insulation SOLARCORE® Aerogel insole provides underfoot superior warmth while being extremely flexible and ultra-thin 100% Recycled mesh footbed cover Cleansport NXT™ treated for natural odor control 50% Recycled removable PU footbed FloatPro™ Foam midsole for lightweight comfort that lasts Vibram® Icetrek outsole designed to provide the improved grip on very cold, icy, or snowy surfaces Vibram® traction lugs specifically designed to increase traction and shed debris with each step Product Features: Insulation:200 g Primaloft® Gold Eco Upper:Waterproof Full Grain Leather; Knit Footbed:Polyurethane, removable Lining:100% Recycled Mesh Insole:SOLARCORE® Aerogel Weight:1 lb. 3.4 oz. (540 g) Outsole:Vibram® Icetrek with 5mm lug traction on cold, icy, snowy surfaces Midsole:FloatPro™ Foam Insert:Waterproof, breathable membrane Height:Stack Height: 28.5-20.5mm; Drop: 8mm Merrell Women's Siren 4 Thermal Mid Zip Waterproof Boot