These are magnetically mounted frag plug rack for marine aquariums. They were printed in PLA, but I suggest ABS or PETG for the longest life.

Uses 32mm x 2mm rare earth magnets, available from numerous online sources. Mine came from Amazon.

The magnets were coated in aquarium silicone, then glued in their holders. After several days to dry they were coated with multiple coats of black spray-on plasti-dip. For my next build, I'll use the solid plasti-dip and simply dip in the magnets.

Note: Fits most plugs, but not the 1/2" ones. Holes are 10mm, which is a good fit for most of the plugs I have found. I'm using the Oceans Wonders coral frag plugs in the picture: Amazon Link

I'm hoping that will seal them enough to last, but no promises.

Files if you'd like to print your own:

Thingiverse: Frag Rack, Corner

Thingiverse: Frag Rack

If you'd like someone to print one and mail it to you, please contact Greg: Another DIY Guys Printing Service

Greg knows reef tanks and printing, and will make sure you get a good print the first time.