I designed these to fit my Neptune 3 Pro and to include holes for magnets.
If you have the Neptune 3 Pro, be sure to use the Main files ("trimmed" in file name).
If you have a Neptune 4 Series. Make sure the aux fan clears the brackets first. You can either resize them to shorten their height (if you do, lower the hole a bit and then the height of the main part.) You can also make the flat base a bit thicker (which I tried and it worked). Or third option is to add several pieces of VHB tape to lower it's height. That may be the easiest, but possibly the least long-term effective.
However, they should fit most printers. I provided the versions that were left non trimmed from the original model. They do have the holes for the magnets, and improved thickness. I just didn't shorten them. You can choose to resize them how you prefer, with the Fusion Files.
The holes are precise to fit 6x2 magnets.
Settings I used: 0.4mm Nozzle, 0.2 Layer Height, PETG+
I also did these in PETG, which is fine as well.
I used VHB tape as seen in the image, to stick them to the bottom of the heat bed.
Also, I used acrylic glue to hold the magnets in, even though it's a good fit.
The author remixed this model.
Modified to add holes for 6x2mm magnets, improved thickness, and to fit the Neptune 3 Pro. Though these should work for most printers.