ER Collets snap into the eccentric ring inside the collet nut. They are difficult to remove if you do not know this simple trick.
Step 1: Line Up Diamonds/triangles on the Collet and the Nut
Align the laser etched diamonds or triangles (different on various brands) on the collet and the collet nut.
Step 2: Push Down on the Collet.
Holding the collet and nut with the diamonds/triangles in the 12 o'clock position, press down on the collet.
Step 3: Snap Out the Collet.
The collet will snap out easily.