Extreme is a warm thermal boot with award-winning design and many smart details - a favorite for both children and parents.Thanks to the design of polyurethane with adjustable cuff, Extreme is waterproof, lightweight and comfortable enough to wear all day. The boot is made of a flexible polyurethane material called Elastopan® and is a 100% PVC-free, degradable material that contains millions of tiny air bubbles and is 40% lighter than PVC and rubber.Viking thermostats provide 2.5 times better insulation than regular PU boots and are twice as durable. Thanks to the wool and polyester lining, Extreme provides effective insulation for the children's feet down to as much as -20 ° C.The boot's sole is made of TPU, which is slightly heavier than PU but is non-slip and very durable. Extreme is a proven and durable winter classic that is perfect for wet, snowy and cold weather.How to find the right size!Shoe size - inside dimensions 21 - 13.8 cm22 - 14.5 cm23 - 15.2 cm24 - 15.9 cm25 - 16.7 cm2