This listing is for a brand new set of Stamped Steel Long Slot style rocker arms that are made in the USA by Elgin Industries compatible replacements for Chevrolet big block 366 CID (6.0L) 1966-1990, 396 CID (6.5L) 1966-1970, 402 CID (6.6L) 1970-1972, 427 CID (7.0L) 1966-1990 & 454 CID (7.4L) 1973-1990. Set comes with 16 rockers, 16 grooved style pivot balls and 16 lock nuts. These rockers are the long slot design needed for increased lift cams and fit the following big block V8 engines in Chevrolet and GMC passenger cars and trucks.