HEYCO 2497 ( HEYCO: DD-625-550 ) HOLE PLUG, NON-METALIC, BLACK, 23/32 INCH OUTSIDE PLUG DIAMETER, FOR 5/8 INCH DIAMETER HOLE. HEYCO PRODUCTS, INC. DESCRIPTION DD-625-550, PART NO. 2497 (BLACK) <<< USE AS COVERPLATE FOR TYPE ET-5, 6, 16 OR 17 AND PL16 INDICATING LAMPS >>>