This is the Fin Alignment Guide from Estes. Suitable for Ages 10 & Older with Adult Supervision for Those Under 12. FEATURES: Fast & accurate fin alignment for three or four finned rockets No more guessing where your balsa fins go, this guide does it all for you Works with 3/32" (2mm) or 1/8" (3mm) balsa Easy to follow instructions are included INCLUDES: One Fin Alignment Guide REQUIRES: Assembly COMMENTS: Due to small parts that could cause a choking hazard please keep away from children 3 years of age and younger For your safety and enjoyment, always follow the NAR Model Rocketry Safety Code while participating in any model rocketry activities tlh 4/15/11 updated tlc 1/10/13