WD21 Caliper Bolt grade/ spec

[3rdtimesacharm]

The bolts that secure the calipers to the steering knuckle are up for replacement. Does anyone know the original Nissan spec?

 

Looking at what's come off on mine, they're hex heads stamped 6 and appear to be 1/2" 20 unf (?) . I would have thought they should be metric M12 1.25 thread. A M12 x 1.25 above 8.8 grade (with a hex head) is a rare thing around here..

 

To add to this, the old bolts wont thread into new/ refurb calipers. Which again makes me doubt the old set up.