We have gotten reports of the mirror optic mounts being stuck or cross-threaded. This is usually rectified by using the included pliers to acheive more positive engagement and more leverage to remove the ring.

NOTE: Never use the pliers to install or tighten an optic retainer, they are for removing stubborn rings (and for Checking And Adjusting Bearing Tension). Use the flat steel 'key' supplied for installing and tightening them.

The optic retaining ring has 2 slots (green) and 2 holes (red). The slots will accept the included removal tool which is normally used when fitting optics. 

This is the tool:

If you find it difficult to remove the ring with the removal tool, you can use the included snap ring pliers, in the 2 holes on the ring, to facilitate the removal.

Turn left to loosen and right to tighten.

Here is what's included with your machine: Nova Series Included Parts