The Siren Thermo boasts a waterproof membrane, 200g/m² synthetic insulation and Solarcore Aerogel insoles. A zipper makes for easy on and off. The FloatPro midsole offers a nice, soft stride feel - your daily range won't be hindered by lack of cushion. - Waterproof structure - Surface materials: leather and beautiful knit cuff - Rubber toe and heel protection - Primaloft Gold Eco synthetic insulation - Fleece liner, recycled fiber - Solarcore insoles - Vibram Icetrek outer sole, purposefully made for winter conditions - Cleansport NXT anti-odour treatment - The laces and webbing are made of recycled materials - Heel stack 28.5 mm, front stack 20.5 mm, drop 8 mm As a fun little detail: the Solarcore material used in the insoles is originally developed by NASA.