This is a large component holder designed to work with tables with magnetic rails. The tray is 30 cm long at its widest and curves in slightly - this does not match curves of accessories for these types of tables. The rail has four holes in it designed to hold a maximum diameter ring magnet of 12mm with a thickness of 3mm. A pilot hole for an M3x0.5 screw comes pre-modeled in the STL. For the prototypes pictured I used these magnets: https://www.amazon.com/dp/B09Y8JC9CH

This is still a prototype. The magnets above are not super strong so they do not "snap" to a metal rail. However, I have found no sagging on my table and it does not jostle free.