These glow plugs are exact replacements for the originals in my 2008 Chevy Duramax. The old ones came out without any problems (beyond accessibility) and the new AC Delco plugs went in very easily. I'd read stories about stuck glow plugs, so I applied a small amount of anti-seize to the threads. Long story short - my check engine light is off and I'm happy. I would recommend these glow plugs to a friend.