.123" larger in diameter than the "raceless" roller axles currently used by some manufacturers Improved inner race-roller design allows use of more, and larger bearings to increase load-carrying surface area, further reducing stress and wear in the critical roller area Redesigned plunger assembly better withstands forces associated with heavy-duty valve springs and cams typically used in high-performance applications Improved metering device precisely controls oil delivery to top end, ensuring rapid lifter pump-up and reducing possibility of oil starvation to bottom end Each lifter body and plunger assembly is selective-fit and then leak down tested to ensure correct operation Tappets come with the HL2T Limited Travel Kit for improved cold starts and high rpm valve timing accuracy Kit of four tappets