The Back on Track Long Johns are now 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. The superior fabric is also much less likely to form piles than polyester due to the polypropylene fabric's longer fibres. However, polypropylene is somewhat less elastic than polyester, so one needs to choose size more carefully. Due to its excellent wicking qualities, this garment is well suited as underwear during physical activity. The men's style partially lined and has extra room in the front, but with a closed fly. The fabric is smooth and soft. Comes in a range of sizes (Extra Small, Small, Medium, Large, Extra Large, XX Large and XXX Large).