Normally made from polyethylene outer skin and polyurethane foam inner core. Cargo ships shall carry no less than the number or lifebuoys complying with the requirements of SOLAS described in the table below. In compliance with requirements it is fitted with a buoyant lifeline. When being in used for operating the quick-release arrangement provided for the self-activated smoke signals and self-igniting lights, the lifebuoy have a mass sufficient to operate the quick-release arrangement or 4 kgs, whichever is the greater.