New Standard T-Series distributor cap.  This is a stock replacement cap.  For HEI distributors (latch screw style).  Fits the following:

75-81 Firebird/Trans Am w/ V8 Pontiac 301, 301 Turbo, 400, 455 engine
77-79 Firebird/Trans Am w/ V8 Oldsmobile 403 engine
77-84 Camaro/Firebird/Trans Am w/ V8 Chevrolet 305 engine

NOTE : About Standard brand products.  Part numbers appendixed with "T" at the end of the part number are their standard replacement parts, some vendors may call this "economy".  Part numbers without the "T" are their professional series.  Keep this in mind when comparing products/prices.