Usable for 1/4 inch / 6.35 mm screwdriver bits.On top of the screwdriver there's a hole for a 4 mm diameter magnet, that holds the bit.
Link for a usable magnet:https://www.amazon.de/Magnettafel-K%C3%BChlschrank-Whiteboard-K%C3%BChlschrankmagnete-Handwerk/dp/B0C81DJZLB/ref=sr_1_15?crid=3UC4XJ3UMYMRH&dib=eyJ2IjoiMSJ9.AontCXfDOqoVJ64DTMNe3Z3lWMaXIKjHeDFPM7LSGVZDVf1sBh_bTXwIyE0tQYAkSSCKU1wPdbY8hdnsSLcjXk09NEZdgeRh2qcsuYRjj0xTn2PRQJYNpBYx3suDuBka8ySYmGoXl4l4YbAMRGMLUI8Rgi_T5m8bYWEqRlMf5zNfvZP80H1tqA7EZEB5_ThXhPe9YkV-sLrWBKaC_JbaCSn8tykkaStuamPVsuPXY_JVBLSzSTDR1qCMWZE48HO1cUGw9V1FUB7lPxCzL-oguskfW_qagsOUk462qhh-r5c.aWcG0gXw2IkKoGsLdeC3yl2a-3E6axYo-Uv8zbE8y7k&dib_tag=se&keywords=4mm+durchmesser+magnet&qid=1721672423&sprefix=4mm+durchmesser+%2Caps%2C120&sr=8-15