This rocket is a "semi-clone" of an Enerjet 2650 sounding rocket from the mid 70's. The original rocket was 2.65" in diameter and 48" long (without the booster) and flew on (3) 29mm motors. The closest tube diameter I could find was BT-80 (2.6") so I guess you could call this rocket a 2600. I used BT-50 tubes (24mm motors) for the 3 motor tubes since I didn't want 8000' flights of the original. Open Rocket estimates flights of 2000' using (3) E9-6 motors.