2 sets of Rochester Precision Optics available. RPO makes lenses that are used in the PVS-31 and GPNVG-18 systems. These sets are compatabile with housings that accept PVS-14 optics. Included with Opfor Night Solutions 3D optimized eyepiece assemblies, these lenses are 30 to 40 percent lighter then milspec and other competing brands. RPO 3.0 offers low edge distortion, lens flare suppression, excellent light transmission, resolution clarity, weight reduction, and a lower eyepiece profile to your PVS-14 compatible night vision system.