True 75 ohm Cophase harness, CB coaxial cable, Belden cable, Amphenol PL-259 connectors, 96% tinned copper braid.
 
How Co-Phase Systems Work
 
Dual Antennas: Two antennas work together to improve signal strength. 
Special Coax Cable: You must use a 75-ohm RG-59 co-phase harness instead of standard 50-ohm single-antenna cable. Standard "T" connectors will not work properly. 
Spacing Requirements: Antennas need at least 5 feet of space between them, though 9 feet provides the best balance and performance. On smaller passenger vehicles, spacing is often too narrow, which creates a directional signal pattern rather than an omnidirectional one. 
Benefits: They excel on large vehicles like semi-trucks, offering a wider front-to-back reach and better performance when a good ground plane is lacking.