AF Combination spannar sets
We sell combination wrench sets for the following nuts and bolts: AF (inch) spanners The tools for UNF and UNC are labeled AF. The abbreviation AF means Across Flat (American), this roughly means "measured crosswise" the wrenches fit UNF and UNC threads. If the caliper indicates 9/16 "(14.2mm) when measuring the head, you should use a 9/16" wrench. So the size of the head is decisive.