2.4GHz single dipole antenna. This is a longer antenna that will allow you to get the antenna element to the optimal position far from components that can shield your reception; the antenna is also a dipole allowing you to get extra range.
Good option for your ELRS receiver.
This is the older style U.FL connector. Production changed around August 2016. The older connector has a diameter of ~3mm. The newer W.FL connector has a diameter of ~2mm and uses a thinner wire.