Castle X Barrier 2 Mens Snowmobile Boot - Gray - (13) INSULATION: 3-Layer Merino wool blend insulation with wicking air mesh & perforated air trap foam. Castle ColdShield Technology: removable insole, wicking wool blend with metallic heat reflecting layer WATERPROOFING: Fully integrated Castle DRY-X waterproof membrane. Weatherproof treated shell materials include 1000D nylon upper with Armstrong PU coated leather