1 Male PL-259 Connector to 2 Female SO-239 Connectors

The T-connector has a couple of main uses.

First, if you want to run dual no-ground-plane antennas you add the T-connector to the back of the radio

and connect the coax from the two antenna leads to the ends of the "T".

Likewise, if you have a standard co-phase installation you can use individual runs of RG-59 A/U to each antenna instead of a pre-made co-phasing harness.

Roadpro Model Number RPM-358