Nut for 12mm brake line bolt
 

The 12 mm bolt that holds the brake line to the front strut is somehow constantly spinning and doesn't torque down, is there any problem with just installing a nut on the other end of it to secure it? And what size and pitch will it be? I must've over tightened

After following a trail of Subaru part numbers, can anyone confirm if m10x1.25 will work fine? Flange nut or just non-flange standard hex?