Use a co-phase harness for dual antenna installations. A single coax is 50 ohms. A co-phase harness is 72 ohms before it splits into 50 ohms for each antenna. This is important for a good SWR. If you try to connect two single coax lengths to a T connector for dual antennas, you may run into high SWR issues.
It is very important to select the appropriate coax for your system and vehicle. It is essential that the end of the coax that attaches to the mount will be compatible with the mount that you select. Be sure to check out our Help Center with information regarding these topics. You can also try to search for your vehicle model to find options.