C2 Corvette 1966-1967 A.I.R. Pump Pulley

The A.I.R. pump is a part of the original emissions system for C2 Corvettes introduced in 1966, mixing air in the exhaust with fresh air to aid with combustion. The A.I.R. pump pulley will keep the pump working properly. 

This part is also commonly called the smog pump pulley.