This is a simple frame for the DKC-Pro cards (if you can't justify buying the X-Rite ColorChecker Passport for 5 times more).

The frame uses eight 5x3mm (diameter x height) magnets to secure the frame. I used a bit of cyanoacrylate glue to secure the magnet (I like Loctite Gel Super Glue).

As with all my models, I include the Fusion model. It should be well behaved if you want to change dimensions.

Pictured is Atomic PETG - printed in two passes, no supports.