MOREL LIFTER SET - LS - SOLID - 5425 The Ultra Pro Mechanical Lifters are made from a billet body with a clipped axle and have 8000+ RPM capability. The .842 & .875 diameter lifters in this series have a .750 diameter roller wheel. The .903 diameter lifters have a .810 diameter roller wheel and the .936 diameter lifters have a .850 diameter wheel. Recommended Spring Pressures are 250-350 lbs Seat Pressure and 600-850 lbs Open Pressure.