The booster section consists of the motor mount, fins, coupler and ejection baffle. The booster section is attached to the shock cord by a 3/16" eyebolt. The booster has two launch lugs for a 1/4" launch rod. I have built three different types of boosters with 24mm, 29mm and dual 24mm motor mounts, as shown below. Click on a picture for more information about that booster.

All of the boosters use the same coupler/ejection baffle. Each baffle has four 1/2" holes drilled in it at 90 degree angles. The baffles are glued into the coupler with an offset of 45 degrees. This prevents most of the hot particles from reaching the parachute section. The eyebolt is attached to the upper baffle, which connects to the shock cord. The parts used for the coupler/baffle and the finished unit are shown below.