It bolts on perfectly fine, Same diameter as the old one, starter gear meshes, the driveshaft coupler fits as well. This is the 18hp flywheel on my 16hp engine. I will look into the aftermarket replacement ring gear. In the mean time I was just wondering if anyone knew how these flywheels are balanced, which would tell me if I can use it or not. If usable I'd prefer to use this one as it has a steel ring gear, and obviously because I already have it on hand.