As an extension, it is simply an extension. In my case, one that got stuck in the K3 pressure washer gun and one that I saw and tried to remove. It fit so tightly that when the extension came out, half of it (a yellow plastic piece) remained inside the gun. I tried to remove it and ended up scratching it, etc. Whether mine is defective or it has a general application issue, I would have been sure it was a cheap Chinese imitation with very poor fit if it didn't say Karcher on it. In conclusion, if it goes in, it will stay there forever...attempting to remove it will cause damage. I am now waiting to see if there is any damage to my pressure washer gun and end up buying a new one...

Update: It is useless and the gun is leaking everywhere, time to get a new one