Top to bottom:
Hollow Probe
Extended Probe
Standard Probe
I'm not a great fan of these either to be honest, I personally prefer the standard profile probe for ease of pellet loading. The idea of these probes is to push the pellet slightly further down the barrel and the probles are also profiled for a better airflow.
There is a small power gain to be had in most cases but as I said earlier I would rather have ease of pellet loading.
