For compressing valve springs with the cylinder head removed from engine. Powerful lever action tool has handle on the outside. Throat depth is 9-3/4 in. Jaws open from 3-1/4 in. to 8-1/2 in. to fit large displacement engines. Any automotive specialty tool will help make an automotive repair or maintenance task easier, but Powerbuilt products take the concept of help a big step further. Every Powerbuilt specialty tool comes with professionally written usage instructions that take you step-by-step through proper tool usage. Photographs of the tool in use accompany the instructions. All developed by an automotive professional who writes and edits automotive service manuals.