New Floor pan plug for most and many of the 70-81 era GM Cars particularly Firebird TA & Camaro
Size to fit a 23mm hole.. or about 15/16th.
This 23mm floor pan plug also matches the Firebird/ probably Camaro rear inner fenders, directly behind tyre.
This metal plug has the 2 small ears under it to press up against the floor to lock them in.