Even your smallest rockets can zipper. So why not protect them with a 

Black Cat Rocketry Mini Ball Anti-Zipper device.

Sized for Mid-power rockets.

The kit includes:

• Small Kevlar sock 
• Foam ball to absorb the shock cord stress to the airframe wall
• 2 cable ties to secure your Mini-Ball to your shock cord.

Assembly is simple.

• make a  hole in the foam ball for your shock cord 
• pass the shock cord through the ball
• fit the Kevlar sleeve over the ball
• adjust the ball position so when the shock cord is at its full stretch position 1/2 of the mini-ball is above the edge of the airframe  (see below)
• attach cable ties and trim cable tie ends

Need a bigger version of this ?  See our friends at Giant Leap Rocketry

Made in Britain by Black Cat Rocketry.