For Big Block Chrysler applications using a retro-fit Hydraulic Roller cam; .904? diameter; 159g weight; 2.63? seat height; Performance replacement for stock Hydraulic Roller lifters or retro-fit Hydraulic Roller lifters for non-roller blocks; Decrease friction and increase longevity when directly compared to flat tappet lifters; Accept much more aggressive cam profiles than flat tappet lifters will allow