This is the BT-20 Model Rocket Body Tubes by Estes. Suitable for Ages 10 & Older with Adult Supervision for Those Under 12. FEATURES: Strong and lightweight tubes Used for custom model rockets or repair work Plain brown tubes with a thin wax coating Can be cut to needed length Works with the NC-20 nose cone INCLUDES: Four BT-20 Body Tubes SPECS: Inside dimension: .710" (18mm) Outside dimension: .736" (18.7mm) Length: 18" (45.7cm) COMMENTS: Use tube couplers to join tubes or to support tubes while cutting to length. JAL 1/22/98 ir/jl UPDATE JMM 2/5/03 updated tlc 12/14/12