This is the pic of the glow plugs as per my forum Topic.Both are the exact same length, however,you will see that on the old one the thread is much shorter..so when fitting the new NGK one,there is about a third of the thread visible.I was going to just see if uit still started with them like this, but surely unless the thread is fully seated,it will affect the compression ?? Any advice would be appreciated.Cheers.Colin