This Extruder Visualizer, unlike most of the others you will find, will help you center your magnet thanks to the centering lip that will also collect the extra glue.

This Extruder Visualizer is also designed to ensure a good clearance between your Nema motor and your Visualizer to make sure there is absolutely 0 friction due to the visualizer.

This visualizer is designer for 8mm diameter magnets.