All the same advantages as Jims Powerglide II tappets, but a hydrosolid design with a special bronze alloy roller bushing in place of stock type loose needle roller bearing for use in High Performance engines with high lift cams. Tappet roller failure is a catastrophic and expensive failure. Broken needle rollers allow the tappet roller to deform, causing cam lobe damage. Pieces of the hard rollers, as well as debris from the cam can easily contaminate other parts, such as cam plates, bearings, oil pumps, and other tappets ultimately resulting in a complete rebuild. This new failsafe design means that, even if the bushing wears out, it will be retained in the tappet assembly. Fits 1999-2017 Twin Cam, 2017 to present Milwaukee Eight, as well as 2000-2022 Evolution Sportster and air cooled Buell. Must install with adjustable pushrods. Sold each.