The Ultra-Pro™ Series is without a doubt the best roller lifter available today. They are engineered to operate flawlessly in ultra-high spring pressure environments, and designed for use with the most radical camshaft profiles. The bodies are FEA-engineered to provide an optimum balance of superior strength at minimum weight. Crane's race-proven Bearing-Focused™ oil system features small channels in the lifter body to lubricate the needle bearings. The roller wheel/bearing/axle combinations are optimized per lifter diameter (i.e. .904” diameter lifter has an .815” diameter wheel).