This was designed to protect a 75mm diameter magnet (about 3in).
The Cone: It prevents the magnet to get stuck (the cheapest solution is to use the top of a bottle). The model is threaded at the base. That's why you also need the "Magnet_Fishing_Thread. stl" file.
The Thread : It's basically a circle with a thread printed around. It will fit perfectly your magnet. I recommend you to use some glue in order to never worry about it. With the cone and the thread you are able to screw both of them on the magnet and take the cone off whenever you want.
- The Coaster: It's just a way to protect the bottom of your magnet and damper it's magnetic abilities. It will still be strong (and dangerous). It just prevents you from inadvertently stuck things on it.
I left the standard parameters and everything was fine.