Estes rockets are grouped into four catagories: RTF (Ready to Fly), ARF (Almost Ready to Fly), E2X (Easy to Assemble) and Skill Levels 1 through 5.
All skill level 1-5 kits require measuring, assembly, sanding, gluing and painting. As the skill level goes up, the difficulty in building skills and time to build and finish is increased.
Skill Level 1-Beginner builder skills.
Skill Level 2-Average building skills.
Skill Level 3-Intermediate building skills.
Skill Level 4-Advanced building skills.
Skill Level 5-Master building skills.