The factor features icebreakers 150gm corespun fabric merino wool fibres wrapped around a nylon core for added strength and durability which retains next to skin softness for the underarm panels they use 120gm eyelet merino mesh fabric to aid in ventilation during high output days bonded seams eliminate chafing while thumbhole cuffs add a touch of warmth and functionality and make for easy layering the deep front zip lets you quickly dump excess heat or manage your body temperature why