OBrien Mens BlackBlue Flex V-Back Life Jacket OBrien Mens Flex V-Back Life Jackets are built for comfort and mobility while out on the water. These life jackets feature wide armholes, segmented panels with multiple hinge points and the Flex V-Back stretch panel to allow the life jacket to move with the wearers body. Its BioLite construction adds breathability for faster drying and exceptional comfort. OBriens BioLite material is lighter and more environmentally friendly than traditional neoprene