The Aeros Premium Traveller Pillow is constructed using an interior bladder welded from a TPU film - it"s lightweight, high strength and performs well in all temperatures. It"s covered pillowcase-style, so the face fabric retains maximum softness. For this Sea to Summit uses an exceptionally soft brushed polyester - a 50 denier knit - for its appropriate durability and its ability to stretch around the TPU bladder without puckering. As for the shape of our Premium Traveller pillow, Sea to Summit opted for very oversized, bulbous "arms" to provide great support to the head. The center of the pillow is quite narrow by comparison, so that there"s support without too much pressure to the back of the neck when pushed against the headrest.