This is the Shock Cord Kit from Estes.
Suitable for Ages 10 & Older with Adult Supervision for Those Under 12.
FEATURES: Contains two 1/8" x 18" and one 1/4" x 36" rubber shock cords
Shock cord mounts included
The shock cord prevents a sudden jolt to the rocket when the
INCLUDES: Three 1/8" x 36" (3mm x 91cm) shock cords
One 1/4" x 48" (6mm x 122cm) shock cords
4 shock cord mounts
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