Friends its too easy to make life rings for our crafts..for 1:28, 1:35, and 1:26th scaled rings we can simply use the rubber O rings used in a sewing machine bobbin winder..can paint it in to any colour..and for tiny crafts can use NCV ( needle control valve) O rings, or MCV ( main control valve) O rings , these valves are used in high pressure L P G applications, to control gas flow, will be easy and in scale..