If you have a 'bolt-on' towball (sometimes called a Witter type) and you have recently bought a caravan with the Alko or BPW stabiliser that is part of the caravan hitch, you will need to have a towball with an extended neck
Using the standard towball you run the risk of damaging the stabiliser because it will not have full articulation on tight corners or over humps in the road.
This is the towball you need. You may also need to put a spacer between it and the towbar to ensure that the stabiliser doesn't foul on the back bumper.
This towball comes complete with the spacer and longer bolts. It is a genuine Alko part.
It's very heavy so it's buyer to collect only I'm afraid