This allows you to put two LoopHoles on one core and spin them at the same time.
After releasing the LoopHole I quickly felt like the buttons needed revamped. From the weight to the small set screw, I just was not 100% happy.
And then the Core was born! It is about half the weight of the original buttons, eliminates the need for a set screw, and slips on/off easily with the two o rings. The o rings are industrial grade and will stand the test of time.