Match Grade Rear Sight 1/4 Minute Conversion Kit. Turn any standard AR rear sight into a match grade 1/4 minute rear sight. Unlike other conversion kits that simply double the number of clicks per revolution, this kit replaces the screw and aperture with finer threaded parts. Your windage knob will have distinct 10 clicks per revolution adjustments but with half the movement. Comes with aperture, windage screw, flat spring, hood and .040" interchangeable iris insert. Other sizes available: .042" and .045". Item RSCONV-IRIS ($8.95 ea.) ********** 28 TPI *********** Yes, this is fine for service rifle class. They don't make a rear sight for AR 15's with the windage knob on the left side. If they did it would not be service rifle legal. What is the size and pitch of the windage screw? The windage screw is 72 tpi. You will have the same 10 clicks per revolution as a standard windage knob but they will be 1/4 minute.