Dan, the bushings were factory installed as far as I could determine. They were flush with the inletting of both tangs. I assume their purpose was to stop over tightening of the rear tang screw. My thinking is that the factory adjusted the clearance by fitting of the sears, if you examine LC single trigger locks you can see that the left sear is different than a double trigger one,(something to be aware of if converting a SST to double triggers). Jim