Rectangular khaki cotton flotation bladder with a small metal inflation valve fitted into one corner. The fabric is heavyweight and waterproofed, consistent with flotation or buoyancy aids used during the Second World War.
The item may have served as part of an emergency life-saving device, possibly issued to aircrew or naval personnel for survival at sea. The compact design allowed it to be folded into survival packs or life vests and inflated manually through the valve when needed.