LaCrosse Men&#39;s 16" ZXT Insulated Knee Boot 100% Rubber Rubber sole Hand-laid premium ZXT Rubber for durable, waterproof protection ZXT Rubber is ozone, abrasion and tear resistant with added tensile strength 9mm wool felt midsole and polymeric foam insulation for warmth around the foot Multilayer rubber on the toe and heel plus a double-layer, ribbed vamp for added durability and support Added layer of knurled rubber under the arch for protection during shovel work