NECG Front Sight Insert Fitting Instructions:

To fit these inserts, simply use a sheet of 220-320 grit sandpaper on a clean, flat surface. 
Set the sight insert down onto the sandpaper. 
Push the sight back and forth several times, being careful to keep the insert straight up. 
From time to time try the insert in the dovetail. 
Repeat as required until the insert slides completely into the dovetail. 
Tip: From time to time tilt the insert @ 45 degrees to the left and right to break the edge of the dovetail. Not all front ramp dovetails have clean, sharp corners. Breaking these edges may be all that is required to fit the insert. 
For the final fitting of the sight insert we suggest some gun grease or oil on the bottom of the sight insert.