The 2x2 or 4x4 D Ring mount plate has many purposes, the most popular is for the ability of using bungee cords to suspend the gyro from the airframe of an aircraft or other mount system. By hanging the gyro this way, the gyro is more free to resist outside forces and you are more free to guide it gently as needed. You are also freed up from the weight of the gyro and camera that can cause fatigue. The D rings are removable and can be positioned as needed in any of the 16 outer threaded holes. The inner circle of holes is how you will attach the plate to the gyro.
The original purpose of the mount ring without the D rings, was to be able to stack two KS4x4 gyros together. You will need two of these plates, one with the 16 holes threaded and the other with the 16 holes with countersunk clearance holes. Ordered separately.