Hydraulic roller lifter retainer kit can be used on all Gen VI 454 and 502 engines that are machined for hydraulic roller lifters. Includes 16 rollers lifters P/N 17120061, 8 lifter guides, 1 lifter guide retainer and 4 retainer bolts. For single service replacement lifter, use P/N 12722013. NOTE: These lifters allow more oil to the rocker arms than the late model truck roller lifters.