This is the B4-4 Standard Model Rocket Engines/Motors from Estes. Suitable for Ages 10 & Older with Adult Supervision for Those Under 12.
Single stage engine
Standard engine designed for flights in rockets weighing less
than 3.5 ounces, including the engine
Engines tested and certified by the NAR
Easy to use and comes with clear instructions
Length: 2.75" (7cm)
Diameter: .69" (18mm)