CLARKS Men's UN.FURL 100% Leather Rubber sole Lambskin lining with reduced stitching surrounds the foot in luxurious softness to prevent irritation and blisters. Removable, vegetable-tanned leather insole reduces foot friction. Unique air circulation system features intake vents to allow cooler, fresh air to enter. Channeled mesh creates a defined path for warm, moist air to flow and escape through exhaust vents. Lightweight ''Ultra Flex'' EVA outsole sole reduces lift load and foot fatigue for all-day wear.