Competition Cams 853-16 Retro-Fit Hydraulic Roller Lifters for Small Block Chevy Non-Roller Engines .842 diameter; 136g weight; 2.49 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