Sorel Boots - Sorel Flurry Boots - Black/ Bright Red :: Boy > Boots. The stretch front shaft guarantees a comfortable fit and seals out cold air It is also crafted with an insulating blend of polypropylene and recycled polyester to trap warm air The recycled felt inner boot is made with wicking polypropylene to wick moisture away from foot Insulation: Removable 6 mm washable recycled felt inner boot Built-in gaiter with barrel lock fastening system and fixed elastic instep strap Sorel Temperature Rating: Able to withstand the coldest conditions ( down to -32 Degrees Celsius) Midsole: 2.5 mm bonded felt frost plug Upper: Durable water and wind resistant PU backed synthetic textile upper Weight: 482 g Enhanced traction with multi-directional lug outsole Outsole: Injection molded waterproof thermal rubber shell The frost plugs are used underfoot to add a thermal barrier between you and the cold ground