>>96366613
I like to use 1/4” donut magnets with a 1/8” hole in them. It’s a bit tricky to drill that large a while in the bottom of most jet bikes, sometimes you split the seam but it’s easy to coverup with a bit of putty.

For vehicles I like to use a thicker rod and magnet, I use 3/8” donut, and then I bought a 1/8” rod and concentric 1/“4 tube. They go like this.