DK-21 and DK-23 compatible circular eyecups
Do you prefer the D800 style circural viewfinder to the standard one on your Nikon Dx000 or D300, D6x0 or D750?
While this is not compatible with DK-17 accessories, it looks good. I stuck a plumber's washer on it too for better finish and in order to avoid scratching my glasses, but it fell off on the D750.
I could not manage to print it in one piece so I have split it in two pieces that are easy to glue together.
Based on https://www.myminifactory.com/object/nikon-dk-21-eyecup-1731