I have had enough frustration with mechanical valve spring compression tools. The jaws are not strong enough and always slip off of the spring. The springs are spherical and at an angle, how do you expect a straight jaw to hold it? Not to mention that extracting the keepers are inhibited by the tool itself. This lever type tool is the easiest and quickest way to remove valve springs hands down! Access to the valve keepers not an issue and you can bounce the spring to assure the keepers are in place. I don't know why anyone would use anything else!