Machine cut aluminum with three adjustment settings and two roller bearings. Why two? 'Cause we like stuff to go twice as fast as everybody else's. Double Roller Bearings assures precise alignment in the frame. We've even re-machined the roll pin (included) to the exact dimension. Most DM4 Triggers come with two set screw adjustments. But since we're on this more kick we've added a third for a Rear Stop Adjustment.