This is the Ultimate Tube Marking Guide from Estes. Suitable for Ages 10 & Older with Adult Supervision for Those Under 12. FEATURES: Works with all Estes body tubes A guide to help with the toughest of measurements INCLUDES: One Ultimate Tube Marking Guide 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 tlc 3/16/12 updated tlc 1/10/13