Seals Thermax Wellington Boots are constructed from Flexplus non-cracking natural rubber featuring 5mm neoprene insulation lining. They're also designed with a waterproof adjustable gusset which allows easy access to the boot and simple adjustment to the calf width for those who require it - all secured by an easy quick release strap. It's easy to see why the Seals Thermax is an enduring favourite welly among the farming and dairy farm communities!