These are three models for cases for 3.5" HDD magnets. The dimensions are in the name of the parts and indicate the dimensions of a rectangle that you could draw around the curved magnet.
These magnets are quite strong but the rounded corners of the case help levering the magnets off of the metal surface.
To get the magnet off of the metal carrier that they are glued on in the hdd, you can use a chisel or a knife, but be verry careful. I clamped the metal part of the hdd magnet in the vise and used a chisel to losen the magnet from its carrier. Like this my hand was no-where near the possible path of the blade.
When slicing the model, go to the layer preview and add a pause right before where the cavity will be closed up with the next layer. At this point you can put the magnet in and continue the print.
The author marked this model as their own original creation.