RPO ZR2 was a special off-road/suspension package offered by General Motors primarily on their 4x4 2nd Generation S-Series line.
Base 2WD models came with 15x6.5-inch wheels with directional vents, Xtreme and ZQ8 models came with 16x8-inch wheels while 4WD models (including the ZR2) used 15x7-inch wheels.