Thanks Harry, Francis, my engine is ABC and has no ring, sorry. It is a .50CXTN, on Fox 5% fuel/20% castor it turned the Graupner 12x5 at 12,195 rpm. Just when I fired it up my neighbor showed up with a load of firewood so it was nearly dark when I got to try it again. It weighs 1lb .5oz with muffler and prop nut and washer. I'd bet the ringed one weighs exactly what they claim.