The transition piece is essentially a 3-in-1. It holds the camera, and acts as a baffle, all while transitioning from a large tube to a small tube.
The launch lug has a mushroom shape that allows it to fit in the rail launchpad without getting stuck. There are two launch lugs that are slightly spaced out so that the rocket will fly straighter as it takes off.
The motor mount consists of two pieces. The top portion holds the motor, while the lower portion acts as a key, keeping the motor inside the rocket. The bottom of the larger portion of the motor mount has a hole at the bottom that consists of a circle and a rectangle. Perpendicular to rectangle cutout, there are two small rectangular prisms that stick out to stop the "key" from spinning 360 degrees. The "key" has an extrude that matches the cutout in the other portion of the motor mount but is scaled down so it fits inside. It also has a smaller circle cutout that goes all the way through so the motor can still be ignited and expel it's charge.