I have an 11 year old BVM F4. One of the toughest built models I have ever owned. It's heavy metal and flues like it, but got years I have flown it like a sport jet. I would build another in a heartbeat. It is a kit and is definetly a build job but the BVM manual is excellent. I have converted several from ducted fan to turbine over the years. Another arrives next week for similar treatment.