Round window on Wolfholm There is a round window in the Wolfholm build by Jonas Kramm.  It's on the left side, top floor. Can anyone identify the round white piece and the smaller round black piece inside. (might be a pulley).
The obvious part is Technic, Wedge Belt Wheel (Pulley) as Phil mentioned in the comments.

Other, not so obvious piece is Brick, Round 4 x 4 with Recessed Center, which comes in new Minions set. It only comes in Light Bluish Gray [BL] color at this moment.

Jonas has confirmed this over his IG post:

It's a Minion Eye.