What is the difference between IPEX1 and IPEX4, and UFL for antenna connectors?

Just a quick question as I am not sure how to tell the difference between IPEX1, IPEX4, and U.FL as they all look the same to me when trying to buy a set of antennas online?

IPEX1 and U.FL are essentially the same connector, just made by different brands, they are interchangeable and the most common type used on ELRS receiver and TBS crossfire etc…

IPEX4 is slightly smaller and use on some Frsky/Futaba receivers

The image below shows the differences side-by-side, so hope that helps!