For balls, they can be designed to be secured by screws, or have the thread at one side with a hole for the screw driver. Like as shown in the picture.

Two types of balls

Balls insertion tool

The advantage for the hex type is easy to install. You can hold the screwdriver with the ball in one hand, and the other hand holding the parts to secure the ball. It is widely used in the 450 class heli.

But in the 300 class, the ball is smaller, and the neck of the ball is small as well. So, you can find that the biggest complain is the during a crash, the neck is broken and the thread is left in the parts. Then your parts become useless, and is having great cost if it is a CNC one.

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