US Flange Bolt Head Wrench Size

Head/Wrench Size*
Flange Bolt DiameterHex Flange Bolt (IFI-111) and Hex Flange Lag
1/4″3/8″
5/16″1/2″
3/8″9/16″
7/16″5/8″
1/2″3/4″
9/16″13/16″
5/8″15/16″
3/4″1-1/8″
* This is the width across the flats.