What airplane will it go on? gwsdrgnfly gave some solid advice. For 3d the APC's wide series seem to work well, but many like the narrow 13X6, depending on what flavor of 3D you are doing, and with which airplane. I am comparing this to my Magnum and OS .61 engines, and Magnum .75 engine. Won't own any more Tower engines, bad experience with them, but their mufflers rock, exspecially on .46's.