Laptop vesa mount adapters for attaching a laptop to a monitor arm*. There are multiple versions, one for a 2013 retina macbook pro, and generic ones for thinner laptops (about 12mm base or thinner) and thicker laptops (15mm base or thinner). I've only printed and used the first one.
I've used it with an Ergotron LX Monitor Arm* and a North Bayou Monitor Arm*. They both work, but Ergotron arm has a wider range of motion / positions, the North Bayou arm is a lot cheaper. The Vesa screw locations are placed to avoid interfering with the motion of the Ergotron arm.
It also needs four M4 flathead screws and four nuts (preferably wingnuts).
-- Atomic Filament Sapphire Blue PETG