I have had several sets of spring compressors and they all seemed life threatening. So I splurged on them a little. Pep Boys wanted to spend over a thousand to replace 4 shelves so I bought this and glad I did. It made that job as simple as changing spark plugs. I fastened it to my vise, put in the spring and post and hit it with one punch, and in a few seconds the spring was compressed. Pulled the frame out and put a new one in. A must for the DIY workshop. Just note that the case is the size of a cooler, so make room.