The Facom EH.6 standard bits series for countersunk hex head screws has a drive size of 1/4 inch.
Hex size 4 mm
Hexagon Screwdriver Bit, 4 mm Tip
£ 8.84
Checking for live stock
Head Type:
Hexagon
Type:
Driver Bit
Size:
4 mm
3D Model:
https://www.traceparts.com/els/rs-components/en/api/viewer/3d?SupplierID=RS_COMPONENTS&PartNumber=2381987&DisplayLogo=False
