Both building and flying js3. Even though the Ziroli Jug is "only" 7 inches bigger than the TF kit the airplanes' volume is much greater. The Ziroli Jug will easily swallow a G-38 gas burner and will finish out at 16-17 pounds compared to about 12 for the TF airplane. Out at the field it commands more attention, IMHO, than the smaller TF kits as well. It's just apparent the airplane is no longer in the same class as the .60 size fighters.