Procomp Electronics 4340 chromoly steel roller tip rockers have a long slot and are for high lift cams to stand valve spring pressure up to 350lbs. A self-locking nut and powdered metal pivot ball are included with rocker. One way to increase power is to increase lift. That's what makesProcomp Electronics steel roller tip rocker arms so popular. They're one of the highest lift rockers you can get outside of racing. And, along with the lift, you also get a ball pivot roller tip to prevent valve stem and guide wear.