You are bidding on one NOS GM rear axle vent, part 3820840 group 5.387. This is correct for all 1964 1965 1966 1967 1968 1969 1970 1971 1972 Chevelle Impala Nova Camaro Monte Carlo cars with 10 or twelve bolt rear end. This the correct all white one not the later produced one with the green top that I have seen listed to fit these cars. This is what your car would have left the factory with, and are get very very hard to find. Please look at the second picture, my camera doesn't do the greatest  on close ups but you can see that it has DANCO PAT-NO 3-021-029. You can buy the after market white ones now but they do not have the stamping on them as the originals did.  Any questions just ask. box not included as their was more than one to a box. Happy Bidding!!!!!