Changing the spark plug on my 2006 F150 5.4 got stuck and I rounded off the collar but didn't crack the spark plug. I used a good tooled electric percussion gun. The cork got stuck because I had no way had to pick it up and loosen it from the cylinder, other than breaking and removing it with special tools and a skilled process. The Irwin 9/16 seemed to dull a bit after only using it once, which is acceptable. I like how the inside of the socket area narrows as the breech moves up the socket as the user rotates the tool, making it more secure. , but I needed a deep well, but there wasn't one. The Irwin clasp is of good quality and heavy weight. Buy a set if you want to save. Certainly a quality tool. Make sure you use an impact gun with a tool for a higher success rate. This worked for me.