Valve stem seal.
Sold in singles.

To fit:
911 1978-1989 12 per engine
911 (930) Turbo 1978-1989 12 per engine
911 (964) C2/C4/RS 3.6 1989-1994 12 per engine
911 (964) Turbo 3.3 1991-1992 12 per engine
911 (964) Turbo 3.6 1993-1994 12 per engine
924S 2.5 1986-1988 8 per engine
944 2.5-2.7 1982-1989 8 per engine (not S/S2/Turbo models)
928S 4.7 1980-1986 16 per engine