The "Nocs" Sighting System is a visual enhancement attachment utilized by mobile frames to increase weapon accuracy.
|“||The RD-214 “Nocs” sighting system attaches easily to the head of most frames, enhancing the accuracy of the frame’s weapon systems for the range at which the sensors are calibrated.||”|
–Mobile Frame Zero: Rapid Attack rulebook, pg. 85
Main Source: Mobile Frame Zero: Rapid Attack Rulebook