This is a legobrick servo adapter for MG996R or similar so you can use big servos on your legotechnic projects.

You can use it as a normal servo or as a 360 servo with the gear included.

I used it to make a small rc car with one servo for steering and one for drive (360 degree servo).

If the holes are too small or not round enough just use a 5mm/4.8mm drill bit to clean them up.