Why would I use a solid lifter compared to a hydraulic one? Well the the rb25 Head is designed from the factory as a hydraulic setup is what this plunger is right here this is basically designed to actuate the valve itself oil fills physically in the body of the lifter and basically it just causes the lifter to pump up and actuate the valve as opposed to a solid setup where the plunger itself won't even be there it's a solid piece all the action is 100 mechanical no hydraulic whatsoever now what's the benefit of that ? why would the benefit of running a solid lifter like the rb26 setup is from the factory right is that you don't have problems with the lifter trying to keep up with the rpm of the engine , typically on a hydraulic lifter setup majority of your engines are limited to anywhere from 65 to 7000 rpm a lot of guys with rbs that run the hydraulic setup with the 25 heads are still spinning eight to nine , stock lifters are usually pretty good a lot of guys do end up switching over to a solid from a 26 head into a 25 head once they once they really beat on it , it is an option to do that it drops straight in it's not a problem to do