The Long Johns are also available in a 100% polypropylene fabric. The polypropylene fabric's unique advantage is that it is both extra durable and very effective at wicking away sweat and humidity. It also is much less likely to get burled than polyester as the polypropylene fabric has much longer fibres. However, polypropylene is less elastic than polyester, so one needs to chose size more carefully. The fabric is smooth and soft.