These slick, flush-mount gas caps combine the high-tech look of aviation style fuel fillers with a built in trim ring which protects the painted surface around the filler opening from damages and gas stains. A keyed entry system permits their ultra thin profile and prevents unauthorized gas refilling. Installation is thinkable easy and requires no cutting. The outer ring fits into the original filler thread with the actual filler cap screwed into a thread in the outer ring. They are available for all tanks with screw-in style filler openings, vented and non-vented, for Fat Bob style tanks and other tanks with a flat surface surrounding the filler hole.